Bicyclic carbohydrate-derived scaffolds for combinatorial libraries

Article abstract of DOI:10.1016/j.bmc.2005.12.055

A bicyclic scaffold derived from the natural monosaccharide d-glucose, and possessing several diversity sites, was linked to various resins through the primary (C-6) hydroxyl and decorated on the solid phase: the hydroxyl group at C-4 was functionalized a

Full text of DOI:10.1016/j.bmc.2005.12.055

Bioorganic & Medicinal Chemistry 14 (2006) 3349–3367
Bicyclic carbohydrate-derived scaffolds for combinatorial libraries
Giovanni Cervi,b,c Francesco Peri,a Carlo Battistini,b Cesare Gennaric
and Francesco Nicotraa,*
a
`
Dipartimento di Biotecnologie e Bioscienze, Universita degli Studi di Milano-Bicocca, Piazza della Scienza 2, I-20126 Milano, Italy
bNerviano Medical Sciences, Department of Chemistry, Viale Pasteur 10, 20014 Nerviano, Italy
`
Dipartimento di Chimica Organica e Industriale, Universita degli Studi di Milano, Via Venezian 21, I-20131 Milano, Italy
c
Received 2 September 2005; revised 22 December 2005; accepted 23 December 2005
Available online 24 January 2006
Abstract—A bicyclic scaffold derived from the natural monosaccharide D-glucose, and possessing several diversity sites, was linked
to various resins through the primary (C-6) hydroxyl and decorated on the solid phase: the hydroxyl group at C-4 was functionalized
as ester, ether, and carbamate, the amino group in the second cycle (C-30 position) was functionalized as amide, sulfonamide, and
ureido- and thioureido-derivatives. The compounds synthesized on the solid phase were tested for their antiproliferative activity on
tumor cell lines.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
binatorial chemistry approaches.6 Hence, recent efforts
have focused on developing efficient methods of selective
protection, deprotection, and functionalization, both in
solution and on solid supports, to build up libraries of
compounds based on carbohydrate scaffolds. It has also
been reported that, according to Lipinski’s ‘rule of five’,7
the high number of hydrogen bond acceptors and do-
nors in carbohydrate scaffolds can decrease their cellular
and tissue absorption.8 This problem is often bypassed
in the case of monosaccharide-derived drugs by the pres-
ence of specific biological transporters that improve cel-
lular uptake.8
In the current era of genomics, proteomics, and other
-omics, the exponential increase in potential therapeutic
targets is placing an ever-growing demand on access to
novel and diverse chemical libraries. Even though phys-
icochemical and particularly biological properties are
hard to correlate with molecular properties, many mod-
els exist which employ a set of 1D (physicochemical), 2D
(topological) or 3D (geometrical) descriptors to assess
molecular diversity or similarity.1–3 One way to interpret
molecular diversity is to divide it into a functional and a
structural part, and then reduce the structural part to
just the rigid portion of the scaffold. A monosaccharide
is an ideal chiral scaffold containing five functionalized
positions. In principle, various substituents can be
appended at each position and the stereochemistry at
each center can be altered. Sugar scaffolds provide an
unparalleled opportunity to generate libraries of high
functional and structural diversity.4 Indeed, the last dec-
ade has witnessed new roles of carbohydrate chemistry
in the drug discovery process. In fact, the sugar template
has been used as a tool to generate new drugs by first
mimicking non-carbohydrate structures such as pep-
tides.5 More recently, it has been used as a structural
scaffold bearing pharmacophoric functionalities in com-
In order to increase the conformational rigidity of carbo-
hydrate derivatives as scaffolds for the production of li-
braries, and to generate original molecules, the
formation of a second cycle in the sugar skeleton is desir-
able. Examples of this strategy have been already pro-
posed by some of us9 and by others.10 According to this
strategy, we envisaged that fused perhydrofuropy-
rans11,12 could be appropriate scaffolds to develop a li-
brary and to generate diversity through their
functionalities. The conformational rigidity of very simi-
lar sugar-derived bicyclic scaffolds has been proved by
molecular modeling studies and NMR analysis in
solution.9b
In this paper, we describe the synthesis of derivatives of
the sugar-based cis-fused perhydrofuropyrans 1 and 2
(Fig. 1), and their decoration with different functional
groups both in solution and in the solid phase. A library
Keywords: Carbohydrate; Scaffolds; Solid phase organic chemistry;
Antitumor.
*
Corresponding author. Tel.: +39 02 64483453; e-mail: francesco.
peri@unimib.it
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.12.055

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G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
ence of trimethylsilyltriflate, with concomitant O-desily-
OH
lation at C-6, to afford the a-C-glucoside 6 (72% yield).
When performing the work-up of the C-allylation reac-
tion (leading to compound 6) on a large scale, migration
of the PNB ester from C-4 to C-6 was observed. We
avoided this undesired side reaction by quenching the
crude reaction mixture with an aqueous sodium acetate
solution, thus maintaining the aqueous phase buffered at
pH P 5. The same allylation reaction was conducted
directly on compound 3, and afforded the a-C-glucoside
7 (78% yield) with two free hydroxyl groups (at C-4 and
C-6), which was used to investigate the possibility of a
regioselective attachment of the scaffold to the solid sup-
port. Treatment of compounds 6 and 7 with iodine in
dichloromethane resulted in the debenzylation–cycliza-
tion reaction leading to the bicyclic iododerivatives 8
(61% yield) and 9 (74% yield), respectively, as mixtures
of diastereoisomers at C-20 (diastereomeric ratio 3:1 in
favor of the R-isomer determined by 1H NMR spectros-
copy) (Scheme 2). Finally, nucleophilic displacement of
the iodide with tetrabutylammonium azide (n-Bu4NN3)
allowed the synthesis of azides 10 (42% yield) and 11
(quantitative yield), both as mixtures of diastereomers
which can be separated by column chromatography
(Scheme 2). The azido-derivatives (10 or 11), as 3:1 dia-
stereomeric mixtures, seemed to be the ideal candidates
for the generation of the library, possessing three
hydroxyl groups and a masked amine (azide) which
can be orthogonally functionalized.
O
HO
HO
O
1 (2'R)
2 (2'S)
NH2
Figure 1.
of 37 different compounds was prepared and tested on
tumor cell lines, namely colon carcinoma cells (HT29)
and prostatic carcinoma cells (DU145), for their anti-
proliferative activity.
2. Results and discussion
2.1. Synthesis in solution of the bicyclic core
Orthogonally protected derivatives of the bicyclic scaf-
folds 1 and 2 were first synthesized in solution. Commer-
cially available methyl a-D-glucopyranoside was reacted
with benzaldehyde dimethylacetal in the presence of
camphorsulfonic acid (CSA) in acetonitrile (MeCN) to
give methyl 4,6-di-O-benzylidene-a-D-glucopyranoside,
which was benzylated (BnBr, NaH in DMF) (Scheme 1).
The benzylidene ring was then hydrolyzed under acidic
conditions (90% TFA in dichloromethane) to afford
compound 3, which was regioselectively silylated at the
primary hydroxyl on C-613 with tert-butyl-dimethylsilyl
chloride (TBDMSCl) in the presence of imidazole to
give compound 4 (86% yield). The free hydroxyl group
of 4 was protected as p-nitrobenzoyl (PNB) ester to yield
compound 5 (quant. yield), which was allylated at the
anomeric carbon with allyltrimethylsilane in the pres-
2.2. Preliminary solid phase studies
We envisaged a number of possible intermediates which
could be linked to the solid phase. Desilylated 5, namely
methyl 2,3-di-O-benzyl-4-O-(4-nitrobenzoyl)-a-D-gluco-
pyranoside, could be linked to the resin through its
C-6 position and reacted on the solid phase to obtain
resin-bound 6, 8, and 10. We tried to link this
OH
OH
O
i, ii, iii
O
HO
HO
HO
BnO
OH
OBn
OMe
OMe
3
4
iv
86%
OTBDMS
OTBDMS
O
vi
O
v
PNBO
HO
BnO
78%
BnO
quant.
OBn
5
OMe
OBn OMe
vi
72%
OH
OH
O
O
PNBO
BnO
HO
BnO
OBn
OBn
6
7
Scheme 1. Reagents and condition: (i) PhCH(OMe)2, CSA, MeCN; (ii) BnBr, NaH, DMF; (iii) 90% TFA, CH2Cl2; (iv) TBDMSCl, imidazole, DMF,
ꢀ40 ꢁC; (v) PNBCl, CH2Cl2, Py; (vi) allyltrimethylsilane, TMSOTf, MeCN.

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3351
OH
O
OH
O
PNBO
BnO
HO
BnO
i
i
7
6
O
O
61%
74%
R
R
8
R = I
9 R = I
11 R = N3
ii
ii
100%
42%
10 R = N3
Scheme 2. Reagents and condition: (i) I2, CH2Cl2; (ii) n-Bu4NN3, toluene, 60 ꢁC.
monosaccharide to different types of resins through its
primary hydroxyl group. Diisopropylsilyl chloride poly-
styrene resin did not show any appreciable loading, while
trityl chloride resin gave an apparent loading of about
46% (based on product recovery after cleavage). Trichlo-
roacetimidate-activated (TCA) Wang resin14 gave the
best loading results (70%), again calculated by attachment
to the resin, cleavage, and product recovery. We then ex-
plored the possibility to perform on the solid phase the
synthetic pathways described in Schemes 1 and 2. Howev-
er, the allylation on the solid phase, using different Lewis
acids (TMSOTf, BF3-Et2O, and SnCl4) and in different
solvents (THF, acetonitrile, and CH2Cl2), gave negative
results (no reaction or cleavage of the starting monosac-
charide from the resin). Therefore, we decided to load
on the resin the allyl C-glucoside 6, which is downstream
in the synthetic pathway. The allyl C-glucoside 6 was an-
chored to a Wang resin affording 12 with high loading.
Resin 12 was used to investigate the feasibility of the iod-
ocyclization reaction and decoration at C-4 on the solid
phase, as shown in Scheme 3.
Hydrolysis of the p-nitrobenzoyl ester and subsequent
etherification at C-4 (for example with a n-butyl group)
gave 14, which was then cyclized to the bicyclic iodode-
rivative 16 (Scheme 3). This process was successful on
the solid phase and the high yield was witnessed by
the substantial recovery of compound 17 after cleavage
from the resin. However, the subsequent conversion of
iodide 16 into the corresponding azide was problematic,
suggesting to consider the direct loading of azide 10
onto the resin as a valuable alternative.
O
O
O
O
i
PNBO
BnO
HO
BnO
OBn
OBn
13
12
100%
ii
O
O
O
RO
BnO
O
iii
RO
BnO
O
100%
OBn
14 R = C4H9
I
16 R = C4H9
iv
iv
OH
OH
O
O
RO
BnO
RO
BnO
O
OBn
15 R = C4H9
I
17 R = C4H9
= Wang resin
Scheme 3. Reagents: (i) KOtBu, DMF or NaOMe, MeOH, THF; (ii) n-BuBr, KOtBu, DMF; (iii) I2, CH2Cl2; (iv) 10% TFA, CH2Cl2.

3352
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
2.3. Solid phase library synthesis
carbamate 22 was accomplished by reaction with p-
nitrophenyloxycarbonyl chloride and subsequent treat-
ment with a primary amine. After derivatization of the
hydroxyl group at C-4, the azido group was converted
to the corresponding amine by reduction with SnCl2,
thiophenol, and triethylamine or by reaction with tri-
phenylphosphine in the presence of water (this methods
turned out to be more efficient). The primary amines 21
and 23 were then derivatized in different ways to deco-
rate the second diversity site, as shown in Table 1.
Bicyclic scaffold 10 bears three hydroxyl groups and a
protected amine (azide) which can be orthogonally func-
tionalized and thus was selected as a good candidate for
developing a library of compounds on solid phase. Our
strategy aimed at the different decoration of at least two
of the four diversity sites of the scaffold. A further point
of diversity is inherent in the structure of 10, which is a
mixture of diastereoisomers at C-20 (diastereomeric ra-
tio = 3:1). We decided to synthesize the library as a mix-
ture of epimers at C-20, taking into account that once a
‘hit’ is hopefully identified during the screening, the two
epimers can be separated and tested singularly. We
decided to use the primary hydroxyl group as anchor
for the attachment to the solid support, with the addi-
tional advantage to have a free hydroxyl group in the fi-
nal compound after the cleavage from the resin, which
might be used to modulate the product solubility. Com-
pound 10 was thus reacted with trichloroacetimidate
Wang resin in the presence of the promoter TMSOTf
to give 18 (Scheme 4).
The amino group of 21 was reacted with different car-
boxylic acids (Table 1) by using three alternative cou-
pling procedures (HBTU, method A; DIC, HOBt,
method B; HATU, method C), with DIPEA as base
and DMF as solvent. Method C resulted to be the more
efficient and reproducible, and it was employed for the
preparation of all amides 24 (Scheme 6). The sulfona-
mides 25 were prepared by treatment with a sulfonyl
chloride, while the ureido-derivatives 26 and the thioure-
ido-derivatives 27 by condensation of the amine with an
isocyanate or an isothiocyanate, respectively. Finally,
reductive amination of the primary amino group of
compounds 21 and 23 with different aldehydes in the
presence of NaBH3CN afforded the secondary amines
28, which were further derivatized by condensation with
a carboxylic acid (HATU, DIPEA) or with an isocya-
nate to give compounds 29.
To optimize this loading, we found that it was possible
to perform a second coupling cycle (after Wang linker
re-activation by trichloroacetimidate formation) with-
out release or decomposition of resin-bound compound.
After the second cycle, the loading of the scaffold in-
creased and reached a value of about 0.60 mmol/g.
Interestingly, the unloaded scaffold was quantitatively
recovered from the effluents (filtrates and washings)
and re-used after purification by filtration through a sil-
ica gel plug. This indicates that it is possible to perform
further coupling cycles on the loaded resin in order to
obtain even higher loadings, if necessary. We set up a
standard procedure comprising two loading cycles.
The Wang resin-grafted scaffold 18 was exploited to pro-
duce a library by taking advantage of the orthogonally
protected hydroxyl group at C-4 of the pyranose ring
and the azido group at C-30 of the furanose ring, which
can be converted into an amino group. Cleavage of the
p-nitrobenzoyl ester was effected with sodium methoxide
in methanol–THF (1:8), affording 19 with the free
hydroxyl group at C-4, which was subsequently decorat-
ed by acylation or carbamoylation (Scheme 5).
Compounds 30–31, 45–48, and 63–66 (Fig. 2) were pre-
pared starting from the Wang resin-bound p-nitro-
benzoate 18 following the synthetic pathways reported
in Schemes 5 and 6.
In order to reduce the number of protection–deprotec-
tion steps in the overall synthetic process, we linked
azide 11, bearing two unprotected hydroxyls, to a silyl
chloride resin (Scheme 7). 1,3-Dichloro-5,5-dim-
ethylhydantoin generated the resin-bound silyl chloride
in situ. This reaction was monitored by IR and the com-
plete absence of the Si–H stretch (2094 cmꢀ1) was
detected within 2 h. The different reactivity between
the primary and secondary hydroxyl groups of scaffold
11 ensured the regioselective attachment to the diethylsi-
lyl resin through the C-6 primary OH to give the dieth-
ylsilyl resin-bound azide 19a with a high loading
(Scheme 7). After a subsequent acylation step, NMR
and HPLC analysis of the cleaved product demonstrat-
ed the high regioselectivity of the loading reaction: the
Esterification was performed with a variety of carboxyl-
ic acids by using diisopropyl carbodiimide (DIC) as con-
densing agent, to afford esters 20. Formation of
CCl3
O
OH
NH
loading = 0.95 mmol/g
O
O
PNBO
BnO
O
TMSOTf
50%
PNBO
BnO
O
O
10
18
= Wang resin
N3
N3
loading = 0.44 mmol/g
Scheme 4.

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3353
O
O
HO
BnO
ii
O
44%
O
i
19
38%
N3
O
O
O
O
O
O
BnO
O
BnO
R
RHN
O
O
20
100%
22
100%
N3
N3
iii
iii
O
O
O
O
O
O
BnO
R
O
O
BnO
RHN
O
O
21
23
NH2
NH2
= Wang resin
Scheme 5. Reagents: (i) RCOOH, DIC, DMAP, CH2Cl2; (ii) p-NO2PhOCOCl, NMM, THF, then RNH2; (iii) SnCl2, PhSH, TEA or PPh3, H2O,
THF.
Table 1. Methods for C-30 amino group acylation in resin-bound compound 21
Method
C-4 substituent
Acylating agent
Coupling reagent
Coupling cycles
Yield (%)a
b
A
B
C
B
C
C
C
p-Nitrobenzoyl
p-Nitrobenzoyl
p-Nitrobenzoyl
p-Nitrobenzoyl
p-Nitrobenzoyl
Naphth-1-ylacetyl
Naphth-1-ylacetyl
Benzoic acid
Benzoic acid
HBTU
DIC, HOBt
HATU
2
1
4
1
5
2
2
15
34
15
27
22
34
Benzoic acid
Caprylic acid
DIC, HOBt
HATU
HATU
Caprylic acid
3,5-(OMe)2PhCOOH
Phenylpropionic acid
HATU
a Yield of the purified product over three reaction steps (azide reduction, acylation, and cleavage).
b Yield not reproducible.
scaffold selectively acylated at C-4 was recovered. The
rest of the library (compounds 32–44, 49–62, Fig. 2)
was synthesized using this modified strategy, which
avoids the steps of PNB ester protection–deprotection
at C-4 required for the Wang-resin supported scaffolds
18 and 19. This simpler and straightforward procedure
also uses milder conditions for the activation of the link-
er and the loading of the scaffold and resulted to be the
method of choice for the synthesis of the library.
A first screening was performed measuring the cell pro-
liferation as percent of a control: selected data are
reported in Table 2. In particular, compound 59 (3:1
mixture of diastereomers at C-20) shows promising
activity on both cell lines. Either one or both diastereo-
mers could be responsible for the activity detected. Now
that a ‘hit’ has been identified, work is in progress to elu-
cidate in detail the structure–activity relationships in this
class of compounds.
2.4. Biological tests
3. Conclusions
All the synthesized compounds (30–66, Fig. 2) were test-
ed against different tumor cell lines. We report here the
antiproliferative activity on a colon carcinoma cell line
(HT29) and a prostatic carcinoma cell line (DU145).
In conclusion, we have developed an original scaffold
derived from the natural sugar D-glucose for combinato-
rial synthesis presenting interesting properties such as

3354
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
O
O
YO
BnO
O
O
24
i
O
YO
BnO
NHCOR'
O
O
ii
O
21Y = RCO
23 Y = RNHCO
YO
BnO
NH2
O
iii
v
25
26
27
NHSO2R'
O
O
O
YO
BnO
O
YO
BnO
O
iv
O
28
NHR'
NHCONHR'
i or iii
O
O
O
YO
BnO
O
YO
BnO
O
O
NHCSNHR'
29
R'
N
COR"
Scheme 6. Reagents: (i) RCOOH, DMF/CH2Cl2, HATU, DIPEA; (ii) RSO2Cl, DMAP, CH2Cl2; (iii) RNCO CH2Cl2, TEA; (iv) RNCS, CH2Cl2,
TEA; (v) RCHO, AcOH, NaCNBH3.
conformational rigidity, multiple and orthogonal func-
tionalization sites, and presence of two similarly reacting
epimers which increase the diversity of the final library.
We explored different alternatives for the synthetic
methodology on the solid phase, setting up a convenient
approach for this scaffold. We have exploited the scaf-
fold in order to generate a library of 37 compounds on
the solid phase, one of which presented promising anti-
proliferative activity on tumor cell lines.
(Merck). The boiling range of petroleum ether used as
eluent in column chromatography is 40–60 ꢁC. Wang
resin (1% polystyrene-divinylbenzene, 100–200 mesh,
0.95 mmol/g substitution) and butyldiethylsilane poly-
mer-bound (PS-DES-SiH) (1% polystyrene-divinylben-
zene, 100–200 mesh, 1.37 mmol/g substitution) were
purchased from Aldrich. HPLC/MS was performed on
a Waters X Terra RP 18 (4.6 · 50 mm, 3.5 lm) column
using a Waters 2790 HPLC system equipped with a
996 Waters PDA detector and a Micromass mod. ZQ
single quadrupole mass spectrometer, equipped with
an electrospray (ESI) ion source. Mobile phase A was
ammonium acetate 5 mM buffer (pH 5.5 with
AcONH4/MeCN 95:5) and Mobile phase B was H2O/
acetonitrile (5:95). Gradient from 10% to 90% B in
8 min, hold 90% B 2 min. UV detection at 220 and
254 nm. Flow rate 1 mL/min. Injection volume 10 lL.
Full scan, mass range from 100 to 800 amu. Capillary
voltage was 2.5 kV; Source temp. was 120 ꢁC; Cone
was 10 V. Retention Times (HPLC rt) are given in min-
4. Experimental
4.1. General methods
All solvents were dried over molecular sieves (Fluka),
for at least 24 h prior to use. When dry conditions were
required, the reactions were performed under Ar atmo-
sphere. Thin-layer chromatography (TLC) was per-
formed on Silica Gel 60 F254 plates (Merck) with
detection with UV light when possible, or charring with
a solution containing concd H2SO4/EtOH/H2O in a ra-
tio of 5/45/45 followed by heating at 180 ꢁC. Flash chro-
matography was performed on silica gel 230–400 mesh
1
utes at 220 or 254 nm. Mass is given as m/z ratio. H
NMR spectroscopy was performed on a Mercury VX
400 operating at 400.45 MHz equipped with a 5 mm
double resonance probe (1H {15N–31P} ID_PFG

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3355
OH
O
RO
BnO
O
NR'R''
30 R=p-NO2PhCO, R' = PhCO, R'' =H
31 R=p-NO2PhCO, R'= nC7H15CO, R'' =H
32 R=1-naphthylacetyl , R'= PhCH2CH2CO, R'' =H
33 R=1-naphthylacetyl , R'= 3,5-(MeO)2PhCO, R'' =H
34 R=cyclopropylCO, R' = iPrCO, R'' =H
35 R=cyclopropylCO, R' = MeOCH2CO, R'' =H
36 R=C2H5CO, R' = iPrCO, R'' =H
37 R=3-pyridylCO, R' = iPrCO, R'' =H
38 R=3-pyridylCO, R' = MeOCH2CO, R'' =H
39 R=3-pyridylCO, R' = Me2NCH2CO, R'' =H
40 R=p-F-PhCO, R' = iPrCO,R''=H
41 R=p-F-PhCO, R' =Me2NCH2CO, R'' =H
42 R=2-thienylCO, R' = iPrCO, R''=H
43 R=2-thienylCO, R' = MeOCH2CO, R'' =H
44 R=2-thienylCO, R' = Me2NCH2CO, R'' =H
45 R=butylNHCO, R' = PhCH2CH2CO, R'' =H
46 R=PhCH2CH2CO, R' = p-MeOPhSO2, R'' =H
47 R=PhCH2CH2CO, R' = PhNHCO, R'' =H
48 R=nC7H15CO, R' = PhNHCO, R'' =H
49 R=p-NO2PhCO, R' = PhNHCO, R'' =H
50 R=cyclopropylCO, R' = iPrNHCO, R'' =H
51 R=cyclopropylCO, R' = m-FPhNHCO, R'' =H
52 R=cyclopropylCO, R' = m-MeOPhNHCO, R'' =H
53 R=C2H5CO, R' = m-FPhNHCO, R'' =H
54 R=C2H5CO, R' = iPrNHCO, R'' =H
55 R=3-pyridylCO, R' = m-FPhNHCO, R'' =H
56 R=3-pyridylCO, R'= iPrNHCO, R'' =H
57 R=p-F-PhCO, R' = iPrNHCO, R'' =H
58 R=p-F-PhCO, R' = m-MeOPhNHCO, R'' =H
59 R=p-F-PhCO, R' = m-FPhNHCO, R''=H
60 R=2-thienylCO, R' = iPrNHCO, R''=H
61 R=2-thienylCO, R' = m-FPhNHCO, R'' =H
62 R=2-thienylCO, R' = m-MeOPhNHCO, R'' =H
63 R=PhCH2CH2CO, R' = PhNHCS, R'' =H
64 R=PhCH2CH2CO, R' = PhNHCO, R'' =Bn
65 R=PhCH2CH2CO, R' = nC7H15CO, R'' =Bn
66 R=PhCH2CH2CO, R' = 1-naphthylacetyl, R'' = p-CH3O-Bn
Figure 2. Library of compounds obtained by solid phase decoration of D-glucose-derived bicyclic scaffold.
1
Varian). Or alternatively, H NMR spectroscopy was
performed on a Varian Mercury VX 300 operating at
300.069 MHz or on a Bruker 200 MHz spectrometer.
13C NMR spectra were recorded on 400 (100 MHz),
300 (75 MHz) or 200 (50 MHz) spectrometers with com-
plete proton decoupling.
59 mmol, 5 equiv) and TBDMSCl (3.03 g, 20.1 mmol,
1.7 equiv) were added under argon atmosphere and
the solution was vigorously stirred at ꢀ40 ꢁC overnight.
The crude was then diluted with 200 mL of CH2Cl2,
washed with water, organic layer dried on sodium sul-
fate, filtered, and concentrated. The product was puri-
fied by flash chromatography on silica gel (petroleum
ether/EtOAc 9:1) and pure 4 was recovered as a colorless
4.1.1. Methyl 2,3-di-O-benzyl-6-O-terbutyldimethylsilyl-
a-D-glucopyranoside (4). To a solution of 312 (4.4 g,
11.8 mmol) in 40 mL of dry DMF, imidazole (4.02 g,
1
oil (5.5 g, 86% yield). H NMR (300 MHz, CDCl3), d
(ppm): 0.10 (s, 6H), 0.90 (s, 9H), 3.37 (s, 3H), 3.48

3356
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
NCl
O
Si
H
O
N
Cl
Si
Cl
quant.
Imidazole, 11
S
i
O
O
HO
BnO
O
19a
N3
Scheme 7. Regioselective loading of the azide 11 onto a polymeric support.
Table 2. Antiproliferative activity of selected compounds on tumor
cell lines
(d, 1H, J = 11.7 Hz), 4.66 (d, 1H, J = 4.0 Hz), 4.68 (d,
1H, J = 11.9 Hz), 4.79 (d, 1H, J = 11.9 Hz), 4.84 (d,
1H, J = 3.4 Hz), 5.17 (t, 1H, J = 9.9 Hz), 7.00–7.60 (m,
10H), 8.00–8.30 (AA0XX0q, 4 H). MS-EI: m/z = 637.4
(M+). [a]D ꢀ23.1ꢁ. Mp = 78.5 ꢁC. Anal. Calcd for
C34H43NO9Si (637.80): C, 64.03; H, 6.79; N, 2.20.
Found: C, 63.98; H, 6.43; N, 2.52.
Compound
HT29
DU145
% proliferation IC50
at 50 lM
% proliferation IC50
(lM)
(lM) at 50 lM
32
33
45
48
58
59
61
44.3
63.5
75.3
75.3
17.9
9.0
>50
>50
16.7
54.7
35.2
49.5
45.8
50.0 63.1
4.1.3. 3-C-[20,30-Di-O-benzyl-40-O-(4-nitrobenzoyl)-a-D-
glucopyranosyl]-1-propene (6). To a solution of 5
(1.46 g, 2.3 mmol, 1 equiv) in 6 mL of dry MeCN, allyl-
>50
>50
32.4
89.3
13.3
1.5
>50
>50
26.3
49.5
32.3
51.7 32.0
trimethylsilane (1.75 mL, 11 mmol,
5 equiv) and
TMSOTf (1.99 mL, 11 mmol, 5 equiv) were added under
argon atmosphere and the mixture was stirred at room
temperature for 72 h. The mixture was then diluted with
AcOEt and carefully kept at 0 ꢁC; then 22 mL of 1 M
aqueous NaOAc, previously stored in ice at 0 ꢁC, was
added. In this way, 22 mmol of base, exactly twice as
much the equiv of TMSOTf, was added, obtaining a
buffer solution (pH 5). Mixing of the two phases, extrac-
tion with AcOEt, washing to neutrality, and evapora-
(dd, 1H, J = 9.7, 3.4 Hz), 3.52–3.62 (m, 2H), 3.80 (t, 1H,
J = 9.7 Hz), 3.80 (d, 2H, J = 5.1 Hz), 4.61 (d, 1H,
J = 3.4 Hz), 4.64 (d, 1H, J = 12.0 Hz), 4.75 (d, 1H,
J = 12.0 Hz), 4.76 (d, 1H, J = 11.5 Hz), 4.97 (d, 1H,
J = 11.5 Hz), 7.20–.60 (m, 10H). MS-EI m/z = 488.5
(M+). [a]D +17.4ꢁ. Anal. Calcd for C27H40O6Si (488.7):
C, 66.36; H, 8.25. Found: C, 66.10; H, 8.16.
tion
afforded
a
crude
mixture
which
by
4.1.2. Methyl 2,3-di-O-benzyl-4-O-(4-nitrobenzoyl)-6-O-
terbutyldimethylsilyl-a-D-glucopyranoside (5). To a solu-
tion of 4 (4.8 g, 9.8 mmol, 1 equiv) in 80 mL of dry
CH2Cl2, pyridine (7.9 mL, 98.0 mmol, 10 equiv) and 4-
nitrobenzoyl chloride (3.6 g, 19.6 mmol, 2 equiv) were
added under argon atmosphere and the solution was
stirred at room temperature overnight. The solution
was then diluted with 100 mL of CH2Cl2, washed with
water, the organic layer was dried on sodium sulfate, fil-
tered, and concentrated. The product was purified by
flash chromatography on silica gel (petroleum ether/
EtOAc 9:1) and pure 5 was recovered as a white solid
(6.2 g, quantitative yield). 1H NMR (300 MHz, CDCl3),
d (ppm): ꢀ0.11 (s, 6H), 0.83 (s, 9H), 3.43 (s, 3H), 3.60–
4.70 (m, 3H), 3.84 (m, 1H), 4.05 (t, 1H, J = 9.6 Hz), 4.56
chromatography on silica gel (petroleum ether/EtOAc
6:4) gave pure 6 as a white solid (880 mg, 72% yield).
1H NMR (200 MHz, CDCl3), d (ppm): 2.51 (m, 2H),
3.61 (m, 2H), 3.70–3.80 (m, 1H), 3.80 (dd, 1H, J = 8.4,
5.1 Hz), 3.94 (t, 1H, J = 8.4 Hz), 4.15 (dt, 1H), 4.66
(ABq, 2H), 4.74 (ABq, 2H), 5.12 (m, 1H), 5.16 (t, 1H,
J = 8.4 Hz), 5.21 (m, 1H), 5.81 (m, 1H), 7.20–7.40 (m,
10H), 8.30 (AA0XX0q, 4 H). HRMS (CI+, CH4) Calcd
for C30H31NO8 [M+H+]: 534.2128. Found: 534.2129.
4.1.4. 3-C-[20,30-Di-O-benzyl-a-D-glucopyranosyl]-1-pro-
pene (7). Compound 3 (9.35 g, 23.95 mmol, 1 equiv) was
dissolved in 51.1 mL of dry MeCN under argon atmo-
sphere. Allyltrimethylsilane (19.27 mL, 119 mmol, 5
equiv) and TMSOTf (21.63 mL, 97.3 mmol, 4 equiv)

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3357
were added and the mixture was stirred for 3 h. The mix-
ture was carefully kept at 0 ꢁC and diluted with AcOEt
(150 mL) and water (150 mL), then Na2CO3 was added
until neutrality. Mixing of the two phases, extraction
with AcOEt, and evaporation afforded a crude mixture
which, by chromatography on silica gel (petroleum
ether/EtOAc 1:1), gave the title compound 7 (7.16 g; 78%
times with CHCl3 and the n-Bu4NN3was recovered as a
colorless oil that became a white solid after removal of
moisture by stripping several times with toluene. The iod-
oderivative 8 (250 mg, 0.44 mmol, 1 equiv) was dissolved
in dry toluene (5 mL) under argon atmosphere, n-Bu4NN3
(375 mg, 1.32 mmol, 3 equiv) was added, and the solution
was stirred at 60 ꢁC for 12 h. The reaction crude was con-
centrated in vacuo and purified by flash chromatography
(petroleum ether/EtOAc 1:1) affording the title compound
10 as a colorless solid (90 mg, 42% yield). Compound 10 is
a mixture of diastereomers that are visible by TLC analysis
(petroleum ether/EtOAc 6:4). 1H NMR (400 MHz,
DMSO-d6); we report the signals of the major diastereo-
mer d (ppm): 1.90 (m, 1H), 2.30 (m, 1H), 3.50 (m, 2H),
3.70–4.20 (m, 5H), 4.2 (m, 1H), 4.67 (m, 1H), 4.75 (ABq,
2H), 5.21 (br t, J = 6.6 Hz, 1H), 7.20 (m, 5H), 8.20
(A2X2, 4H). HRMS (CI+, CH4) Calcd for C23H25N4O8
[M+H+]: 485.1672. Found: 485.1670.
1
yield). H NMR (300 MHz, CDCl3), d (ppm): 2.12 (m,
1H), 2.53 (m, 2H), 3.51 (m, 2H), 3.60–3.80 (m, 4H), 4.02
(m, 1H), 4.65 (ABq, 2H), 4.81 (ABq, 2H), 5.05 (m, 2H),
5.83 (m, 1H), 7.20–7.40 (m, 10H). HRMS (CI+, CH4)
Calcd for C23H29O5 [M+H+]: 385.2015. Found: 385.2016.
4.1.5. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Nitro-benzoic acid 7-benzyloxy-
5-hydroxymethyl-2-iodomethyl-hexahydro-furo[3,2-b]pyran-
6-yl ester (8). To a solution of the C-glycoside 6 (400 mg,
0.75 mmol, 1 equiv) in dry THF (3 mL) cooled at 0 ꢁC
in an ice bath, I2 (570 mg, 2.25 mmol, 3 equiv) was added
and the solution was stirred at 0 ꢁC for 1 h. The crude was
then diluted with AcOEt (100 mL), 200 mL of water was
added and the mixture was vigorously stirred at room tem-
perature adding Na2S2O3 portionwise until the two phases
discolored. The organic layer was washed with water, and
the crude purified by flash chromatography (petroleum
ether/EtOAc 6:4) affording pure compound 8 as a yellow
4.1.8. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),
2-Azidomethyl-7-benzyloxy-5-hydroxy-
6(S),7(S),7a(R)
methyl-hexahydro-furo[3,2-b]pyran-6-ol (11). Compound 9
(670 mg, 1 equiv, 1.60 mmol) was dissolved in DMF
(5 mL) under argon atmosphere, n-Bu4NN3 (900 mg,
3.19 mmol, 2 equiv) was added, and the solution was stir-
red at 60 ꢁC for 12 h. The reaction crude was concentrated
in vacuo and purified by flash chromatography (petroleum
ether/EtOAc 4:6), giving the title compound 11 as a color-
less oil (593 mg, 100% yield). 1H NMR (400 MHz,
DMSO-d6), d (ppm): 1.67 (m, 1H), 2.12 (m, 1H), 3.25–
3.50 (m, 7H), 3.76 (m, 1H), 4.50 (m, 1H), 4.62 (br s,
1H), 4.69 (d, 1H, J = 12 Hz), 4.42 (d, 1H, J = 12 Hz),
5.12 (m, 1H), 7.2–7.4 (m, 5H). HRMS (CI+, CH4) Calcd
for C16H22N3O5 [M+H+]: 336.1559. Found: 336.1562.
1
solid (260 mg, 61% yield). H NMR (400 MHz, DMSO-
d6); we report the signals of the major diastereomer d
(ppm): 2.21 (m, 1H), 2.32 (m, 1H), 3.50 (m, 2H), 3.70–
4.20 (m, 5H), 4.34 (m, 1H), 4.98 (m, 1H), 4.75 (ABq,
2H), 5.21 (br t, J = 6.6 Hz, 1H), 7.20 (m, 5H), 8.20
(A2X2, 4H). HRMS (CI+, CH4) Calcd for C30H31NO8
[M+H+]: 534.2128. Found: 534.2129.
4.1.6. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a (R),5(R),
6(S),7(S),7a(R) 2-Iodomethyl-7-benzyloxy-5-hydroxymeth-
yl-hexahydro-furo[3,2-b]pyran-6-ol (9). To a solution of
compound 7 (1.0 g, 2.6 mmol, 1 equiv) in dry CH2Cl2
(10.4 mL) cooled at 0 ꢁC in an ice bath, I2 (1.32 g,
5.2 mmol, 2 equiv) was added and the solution was stirred
at 0 ꢁC for 3 h. The crude was then diluted with AcOEt
(100 mL), 200 mL of water was added and the mixture
was vigorously stirred at room temperature adding
Na2S2O3 portionwise until the two phases discolored.
The organic layer was washed with water, and the crude
purified by flash chromatography (petroleum ether/EtOAc
4:6) affording the title compound 9 as a yellow oil (800 mg,
74% yield mixture of epimers). 1H NMR (300 MHz,
CDCl3), d (ppm): 2.02 (m, 1H), 2.24 (m, 1H), 3.40–3.80
(m, 6H), 4.05 (m, 1H), 4.54–4.95 (m, 4H), 5.05 (m, 2H),
5.82 (m, 1H), 7.40–7.20 (m, 5H). HRMS (CI+, CH4) Calcd
for C16H22IO5 [M+H+]: 421.0512. Found: 421.0515.
4.2. Resin-linked intermediate 12
Wang trichloroacetimidate resin was prepared starting
from commercially available Wang resin, according to
known procedure.15 The HMP-trichloroacetimidate res-
in (1 g, maximum loading 0.8 mmol) was allowed to
swell for 30 min in dry CH2Cl2 under argon atmosphere.
Then the resin was washed with dry THF to remove the
moisture and suspended in 5 mL of anhydrous cyclohex-
ane. A threefold excess of C-glucoside 6 (1280 mg,
2.4 mmol, 3 equiv) dissolved in 2 mL of anhydrous
CH2Cl2 and a catalytic amount of BF3-OEt2 (25 lL)
were added to the suspension that was shaken for
10 min at room temperature under argon atmosphere.
The resin was then washed with anhydrous CH2Cl2
and THF, and the loading and washing cycle was
repeated by recycling the C-glucoside 6. The resin load-
ed with the C-allyl derivative 12 was finally dried over-
night in vacuo. The loading was determined by
cleaving a part of resin (100 mg) in TFA 10% in CH2Cl2
(2· 30 min, room temperature) and resulted to be of
0.58 mmol/g (average value from three independent
experiments of loading).
4.1.7. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),
6(S),7(S),7a(R) 4-Nitro-benzoic acid 7-benzyloxy-5-hy-
droxymethyl-2azidomethyl-hexahydro-furo[3,2-b]pyran-6-yl
ester (10). The n-Bu4NN3 (caution: explosive if heated in
the absence of solvent) was prepared from the commercial
NaN3 using the following procedure: 40% aqueous n-
Bu4N+OHꢀ (23 mL) was diluted with water (23 mL), a
solution of NaN3 (1140 mg, 35 mmol) in water (10 mL)
was added, and the mixture was stirred for 30 min at room
temperature. The aqueous solution was extracted three
4.3. Resin-linked intermediate 13
4.3.1. Method A. The resin 12 (500 mg, about 0.4 mmol
of bound sugar, 1 equiv) was washed with anhydrous

3358
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
CH2Cl2 (2· 10 mL) and THF (2· 10 mL) under argon
atmosphere in order to remove moisture and then was
suspended in 10 mL of anhydrous DMF and a fivefold
excess of tBuOK (220 mg, 2 mmol, 5 equiv) was added.
The solution turned to a dark blue color and the resin
was stirred at room temperature for 2 h under argon
atmosphere. Three other cycles of hydrolysis of 2 h each
were performed to ensure a complete deprotection of the
position C-4. The solvent was finally removed and the
resin was washed with dry DMF, acetone, THF, and
DMF, affording the resin linked intermediate 13.
mixture was shaken for 2 h and drained. The conversion
was followed by TLC after cleavage of a small aliquot of
resin (10 mg). Other two cycles of reaction were per-
formed. After the last cycle of reaction, the resin 14
was washed with 2· DMF, 2· MeOH, and 3· CH2Cl2.
This method also showed almost complete conversion.
4.5. Iodo-cyclization on solid phase
4.5.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),
6(S),7(S),7a(R) 2-Iodomethyl-7-benzyloxy-6-butoxy-5-hy-
droxymethyl-hexahydro-furo[3,2-b]pyran (17). Resin 14
(400 mg, 0.24 mmol of bound C-glucoside) was allowed
to swell in dry CH2Cl2 for 30 min at room temperature un-
der argon atmosphere then suspended in a solution of io-
dine (300 mg, 1.2 mmol, 5 equiv) in 10 mL of anhydrous
CH2Cl2 and shaken at room temperature for 24 h under
argon atmosphere. The resin was then washed with anhy-
drous THF and CH2Cl2, and another cycle of reaction was
performed. At the end of the reaction, the resin was care-
fully washed with THF, acetone, and CH2Cl2 until the
effluents were colorless and was dried in vacuo overnight
to give the resin 16. A sample of 100 mg of dried resin
16 was cleaved (10% TFA in CH2Cl2, 2· 30 min) and com-
pound 17 was recovered almost pure as judged from a pre-
liminary TLC analysis. Iododerivative 17 revealed to be
resistant to the acidic conditions of the cleavage and was
purified by flash chromatography on silica gel (petroleum
ether/EtOAc 6:4). Twenty-three milligrams of pure com-
pound 17 was recovered corresponding to a loading of
0.5 mmol/g of the resin and to an almost quantitative yield
4.3.2. Method B. Resin 12 (100 mg, 0.45 mmol/g,
45 · 10ꢀ3 mmol) was washed four times with dry THF
to remove moisture, suspended in dry THF (5 mL) un-
der inert atmosphere, and MeONa (625 lL of a 0.5 M
in MeOH, 0.312 mmol, 7 equiv) was added. The suspen-
sion was shaken for 16 h at room temperature and
drained. The resin was washed with 2· CH2Cl2, 2·
DMF, 2· MeOH, 2· DMF, and 3· CH2Cl2, and dried
in vacuo overnight (absence of PNB ester was evaluated
by TLC analysis after cleavage of 10 mg of resin) to give
13.
4.4. Resin-linked intermediate 14
4.4.1. Method A. To a suspension of the resin (670 mg,
0.6 mmol/g, 0.4 mmol) in 10 mL of anhydrous DMF, a
fivefold excess of KOtBu (220 mg, 2 mmol, 5 equiv)
and of n-butyl bromide (215 lL, 2 mmol, 5 equiv) and
a catalytic amount of n-Bu4NI (5 mg) were added and
the mixture was shaken at room temperature overnight.
The resin was then washed with anhydrous DMF, THF,
CH2Cl2, and DMF under argon atmosphere. The O-al-
kylation and washing cycle was repeated two more
times. After the last cycle of reaction, the resin was
washed with DMF, water, acetone, and THF, and dried
in vacuo overnight affording the resin-linked intermedi-
ate 14. One hundred milligrams of dried resin was
cleaved (10% TFA in CH2Cl2, 2· 30 min, room temper-
ature) and the C-glucoside recovered in the effluents
resulted to be almost pure according to TLC analysis.
After purification by flash chromatography on silica
gel (petroleum ether/EtOAc 7:3), 26 mg of pure 30-C-
[2,3-di-O-benzyl-4-O-(n-butyl)-a-D-glucopyranosyl]-10-
propene 15 was recovered, corresponding to a loading of
0.6 mmol/g. 1H NMR (200 MHz, CDCl3), d (ppm): 0.90
(t, 3H, J = 7.5 Hz), 1.30 (m, 2H), 1.50 (br m, 2H), 2.47
(m, 2H), 3.26 (t, 1H), 3.40–3.80 (m, 7H), 4.02 (dt, 1H),
4.64 (ABq, 2H), 4.82 (ABq, 2H), 5.10 (m, 2H), 5.80
(m, 1H), 7.2–7.4 (m, 10 H). HRMS (CI+, CH4) Calcd
for C27H36O5 [M+H+]: 441.2641. Found: 441.2651.
1
of the iodocyclization step. H NMR (300 MHz, CDCl3),
d (ppm): 0.90 (t, 3H, J = 7.5 Hz), 1.35 (m, 2H), 1.55 (m,
2H), 1.94 (dt, 1H, J = 13.0, 6.0 Hz), 2.26 (dt, 1H,
J = 13.0, 6.8 Hz), 3.24 (m, 1H), 3.26 (m, 1H), 3.32 (m,
1H), 3.30 (m, 1H), 3.65 (m, 1H), 3.7–3.8 (m, 4H), 4.00
(t, 1H, J = 5.7 Hz), 4.10 (br t, 1H), 4.56 (dt, 1H, J = 5.7,
6.0 Hz), 4.78 (ABq, 2H), 7.2–7.4 (m, 5 H). HRMS (CI+,
CH4) Calcd for C20H30IO5 [M+H+]: 477.1138. Found:
477.1131.
4.6. Loading of bicyclic azide 10 onto Wang resin
Bicyclic azide 10 (mixture of diastereoisomers) was load-
ed onto Wang resin activated as trichloroacetimidate by
performing two reaction cycles. Wang trichloroacetimi-
date resin (203 mg, 0.95 mmol/g, 0.193 mmol) was
washed several times with dry THF to remove moisture,
then a solution of 10 (470 mg, 0.965 mmol, 5 equiv) in
dry CH2Cl2 (3 mL) was added under inert atmosphere
and the suspension was shaken for 5 min at rt. BF3 Æ E-
t2O (12 lL, 0.095 mmol, 0.5 equiv) was added and the
suspension was shaken for 15 min at rt. The resin was
then washed with CH2Cl2 (2· 3 mL), THF (2· 3 mL),
MeOH (2· 3 mL), and CH2Cl2 (4· 3 mL), and dried
in vacuo overnight. The effluents were collected to
recover the unloaded scaffold 10, which was purified
by filtration through a silica gel plug (petroleum ether/
EtOAc 4:6); weight of recovered 10: 410 mg. To deter-
mine the loading, 49 mg of resin was cleaved with 20%
TFA in CH2Cl2 (2· 5 mL, 20 min) and pure azide 10
was recovered after purification on a silica gel plug
(10.5 mg indicating a loading of 0.44 mmol/g, corre-
4.4.2. Method B. Forty milligrams of resin 13
(0.48 mmol/g, 20 · 10ꢀ3 mmol) was washed four times
with dry THF to remove moisture, suspended in dry
DMF (2 mL) under inert atmosphere, and KHMDS
(152 lL of 15% solution in toluene, 0.10 mmol, 5 equiv)
was added. The suspension was shaken for 15 min and
the excess base was removed by filtration under inert
atmosphere. Butyl bromide (22 lL, 0.20 mmol, 10
equiv) and tetrabutyl ammonium iodide (1.5 mg,
4 · 10ꢀ3 mmol, 0.2 equiv) were added and the resulting

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3359
sponding to a 50% conversion) and fully characterized
by 1H NMR and HRMS. The partially loaded resin
(197 mg; 0.44 mmol/g of loaded scaffold; 0.44 mmol/g
of free OH corresponding to 0.087 mmol of free OH)
was washed, under inert atmosphere, several times with
dry THF to remove moisture, then was suspended in dry
CH2Cl2 (2.9 mL) and trichloroacetonitrile (175 lL,
1.74 mmol, 20.0 equiv) was added. A 1:9 DBU–CH2Cl2
solution (110 lL, corresponding to 11 lL, 0.074 mmol
of pure DBU, 0.85 equiv) was added dropwise in
5 min to the suspension, then the resulting suspension
was shaken for 40 min at room temperature, drained,
and washed with dry CH2Cl2 twice. A second trichloro-
acetimidate formation cycle was performed with the
same procedure, then the solution was drained and the
resin was washed with DMF (2· 3 mL), CH2Cl2
(2 · 3 mL), DMF (2· 3 mL), and CH2Cl2 (4· 3 mL),
and dried in vacuo overnight. The Wang trichloroace-
timidate resin so obtained was washed several times with
dry THF under inert atmosphere to remove moisture,
then a solution of 10 (423 mg, 0.870 mmol, 5 equiv) in
dry CH2Cl2 (3 mL) was added and the suspension was
shaken 5 min at room temperature. BF3 Æ Et2O (11 lL,
0.5 equiv, 0.087 mmol) was added and the suspension
was shaken for 15 min at room temperature. The resin
was then washed with CH2Cl2 (2· 3 mL), THF (2·
3 mL), MeOH (2· 3 mL), and CH2Cl2 (4· 3 mL), and
dried in vacuo overnight to give a batch of the resin-
linked derivative 12a. The effluents were collected to
recover the unloaded compound 10, which was purified
by filtration through a silica gel plug (eluant: petroleum
ether/EtOAc 4:6; weight of recovered 10: 350 mg). To
determine the loading, 68 mg of the resin was cleaved
with 20% TFA in CH2Cl2 (2· 5 mL, 20 min) and pure
azide 10 was recovered after purification on a silica gel
plug (20 mg indicating a loading of 0.60 mmol/g, corre-
sponding to a 78% conversion) and fully characterized
four times with dry THF to remove moisture, sus-
pended in dry CH2Cl2 (1.37 mL) under inert
atmosphere, and 1,3-dichloro-5,5-dimethylhydantoin
(162 mg, 0.822 mmol, 6 equiv) was added. The suspen-
sion was shaken for 1.5 h at room temperature and
drained. The resin was washed with 2· CH2Cl2, 2·
DMF, 2· MeOH, 2· DMF, and 3· CH2Cl2, and dried
by nitrogen flux to get the resin PS-DES-SiCl. Absence
of Si–H (stretching at 2094 cmꢀ1) was confirmed by IR
analysis.
Loading of the substrate: A solution of compound 11
(275.7 mg, 0.822 mmol,
3
equiv) and imidazole
(65.2 mg, 0.959 mmol, 3.5 equiv) in dry CH2Cl2 (4 mL)
was added to the resin PS-DES-Si-Cl (theoretical
0.274 mmol) and shaken overnight under inert atmo-
sphere. The solution was filtered and the unloaded scaf-
fold recovered. The resin was washed with 2· CH2Cl2,
2· DMF, 2· MeOH, 2· DMF, and 3· CH2Cl2 obtain-
ing 19a, directly employed in the further reactions.
4.9. Functionalization of C-4 hydroxyl group, represen-
tative procedures
4.9.1. Acylation. Resin 19 (50 mg, 0.43 mmol/g,
21.5 · 10ꢀ3 mmol) was suspended in dry CH2Cl2
(2 mL) under inert atmosphere and 3-phenylpropionic
acid (32 mg, 0.215 mmol, 10 equiv), DMAP (26 mg,
0.215 mmol, 10 equiv), and DIC (33 lL, 0.215 mmol,
10 equiv) were added. The suspension was shaken for
16 h at room temperature and drained. The complete-
ness of the reaction was followed by cleavage of min-
ute quantities of the resin (<10 mg) and TLC
comparison with a prototype sample prepared in
solution. Typically, the reaction was complete after
one overnight cycle with the quantities described
above. The resin was washed with 2· CH2Cl2, 2·
DMF, 2· MeOH, 2· DMF, and 3· CH2Cl2, and
dried in vacuo overnight (absence of starting material
was evaluated by TLC analysis after cleavage of
10 mg of resin) to give resin type 20. The resin was
cleaved with 20% TFA in CH2Cl2 (2· 0.5 mL,
20 min), and the crude was purified by flash chroma-
tography (4 mg, 38% yield). 1H NMR (200 MHz,
CDCl3), d (ppm): 1.90 (m, 1H), 2.23 (m, 1H), 2.65
(m, 2H), 2.95 (m, 2H), 3.3–3.85 (m, 6H), 3.90 (dd,
1H, J = 7.0, 4.0 Hz), 4.15 (m, 1H), 4.6 (m, 1H),
4.75 (ABq, 2H, J = 12.8 Hz), 4.97 (dd, 1H, J = 6.8,
4.0 Hz), 7.10–7.40 (m, 10H).
1
by H NMR and HRMS.
4.7. Resin-linked intermediate 19
Resin 18 (100 mg, 0.45 mmol/g, 45 · 10ꢀ3 mmol) was
washed four times with dry THF to remove moisture,
suspended in dry THF (5 mL) under inert atmosphere,
and MeONa (625 lL of 0.5 M in MeOH, 0.312 mmol,
7 equiv) was added. The suspension was shaken for
16 h at room temperature and drained. The resin was
washed with 2· CH2Cl2, 2· DMF, 2· MeOH, 2·
DMF, and 3· CH2Cl2, and dried in vacuo overnight
to give 19 (absence of PNB ester was confirmed by
TLC analysis after cleavage of 10 mg of resin). In order
to verify the yield of loading and conversion, the resin
was cleaved with 20% TFA in CH2Cl2 (2· 1.0 mL,
20 min), and monosaccharide 11 was recovered after
evaporation (18 mg). The crude compound was ana-
4.9.2. Carbamoylation. Resin 19 (100 mg 0.42 mmol/g,
4.2 · 10ꢀ2 mmol) was washed with dry THF (4· 2 mL)
under inert atmosphere. The resin was then suspended
in 1.25 mL of THF, and 4-nitrophenyl chloroformate
(85 mg, 0.420 mmol, 10 equiv) and N-methyl morpho-
line (93 lL, 0.840 mmol, 20 equiv) were added. The sus-
pension was shaken for 3 h at room temperature and
drained. A second cycle with the same quantities was
performed for 3 h, then the solution was drained and
the resin was washed with THF (2· 2 mL), CH2Cl2
(2· 2 mL) and THF (2· 2 mL) obtaining the resin–p-
nitrophenyloxycarbonyl derivative. The resin–p-nitro-
phenyloxycarbonyl derivative was suspended in dry
1
lyzed by TLC and H NMR, and then purified by flash
chromatography. Ten milligrams was obtained (66%
yield).
4.8. Resin-linked intermediate 19a
Activation of the resin (PS-DES-SiCl). Resin PS-DES-
SiH (100 mg, 1.37 mmol/g, 0.138 mmol) was washed

3360
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
THF and n-butyl amine (125 lL, 1.26 mmol, 30 equiv)
was added. The suspension was shaken overnight at
room temperature, then the solution was drained and
the resin was washed with CH2Cl2 (2· 2 mL), DMF
(2· 2 mL), CH2Cl2 (2· 2 mL), DMF (2· 2 mL), and
CH2Cl2 (4· 2 mL), and dried in vacuo overnight (ab-
sence of starting material was evaluated by TLC analysis
after cleavage of 10 mg of resin) to obtain a resin type
22. The resin 22 was cleaved with 20% TFA in CH2Cl2
(2· 2 mL, 20 min), and the bicyclic azide with a carba-
mate in C-4 was recovered after evaporation (22 mg).
The crude compound was analyzed by TLC and 1H
NMR, and then purified by flash chromatography
(8 mg, 44% yield). 1H NMR (200 MHz, CDCl3), d
(ppm): 0.92 (t, 3H, J = 7 Hz), 1.25–1.55 (m, 4H), 1.92
(ddd, 1H, J1 = 3.7, 6.5, 11.5 Hz), 2.25 (m, 1H), 3.18
(m, 2H), 3.42 (m, 2H), 3.65–3.9 (m, 4H), 3.97 (m, 1H),
4.18 (m, 1H), 4.63 (m, 1H), 4.7–4.9 (m, 4H), 7.34 (m,
5H).
2 equiv), HBTU (21 mg, 0.056 mmol, 2 equiv), and DI-
PEA (20 lL, 0.11 mmol, 4 equiv) were added and the mix-
ture was shaken at room temperature for 40 min. This
coupling step was repeated twice. The resin was then
washed with DMF (2· 10 min) and CH2Cl2 (2· 10 min)
and dried in vacuum overnight obtaining resin 24
(R = p-nitrophenyl; R0 = phenyl). The IR spectrum of
the resin beads showed the appearance of the C@O
stretching absorption band at 1680 cmꢀ1, typical of sec-
ondary amides in dilute solutions. The amide was then
cleaved treating the resin with 50% TFA in CH2Cl2 (2·
30 min at room temperature) and a few milligrams of
compound 30 were recovered after chromatography (yield
not reproducible).
4.11.1.2. Method B. A solution of benzoic acid
(34 mg, 0.2 mmol, 4 equiv), DIC (43 lL, 0.2 mmol, 4
equiv), and HOBt (38 mg, 0.2 mmol, 4 equiv) in 2 mL
of dry DMF was stirred at room temperature for
20 min. Resin 21 (R = p-nitrophenyl) (95 mg, loading
0.49 mmol/g, 0.046 mmol) was suspended in 1 mL of
dry DMF with DIPEA (96 lL, 0.4 mmol, 8 equiv),
and then the solution of the pre-activated carboxylic
acid was added in the reactor. The suspension was shak-
en at room temperature for 45 min and then the reaction
mixture was filtered, washed with 2· DMF, 2· CH2Cl2,
Et2O, and dried in vacuum for 1 h, obtaining resin 24
(R = p-nitrophenyl; R0 = phenyl). The resin was cleaved
with TFA 20% in CH2Cl2 (2· 20 min) and washed with
2· THF and 2· CH2Cl2. After evaporation of the sol-
vent, 18 mg of crude benzamide was obtained. The mix-
ture was then purified by chromatography on silica gel
(AcOEt/hexane 9:1) recovering mg 4 (15% yield) of pure
benzamide 30.
4.10. Reduction of azido group on solid phase. Prepara-
tion of the resin-loaded aminoderivative 21
4.10.1. Method A. A clear solution of PPh3 (210 mg,
0.8 mmol, 10 equiv), H2O (144 lL, 8.0 mmol, 100 equiv)
in THF (2.9 mL) was added to 200 mg of resin 20
(0.4 mmol/g, 0.08 mmol) pre-swelled in CH2Cl2 for
30 min. The resulting mixture was shaken overnight,
the solution was removed, and the resin was washed
with 2· THF, 2· CH2Cl2, 2· THF, and 2· CH2Cl2.
The TBNS test (visualizing the presence/absence of free
amino groups was carried out as described)16 gave a
favorable result: absence of starting material was evalu-
ated by TLC analysis after cleavage of 10 mg of resin.
After the above-mentioned washing cycles, the resin 21
was kept under inert atmosphere and used immediately
for the next reaction.
4.11.1.3. Method C. A more powerful acylation
method, by using HATU [O-(7-azabenzotriazol-1-yl)-
N,N,N0,N0-tetramethyluroniumhexafluorophos phate,
was also essayed. Resin 21 (R = p-nitrophenyl)
(150 mg, loading 0.38 mmol/g, 0.057 mmol) was sus-
pended in 4 mL of dry DMF–CH2Cl2 1:1 and HATU
4.10.2. Method B. Resin 20 (250 mg, 0.4 mmol/g,
0.1 mmol) was suspended in THF (4 mL) and SnCl2
(152 mg, 0.80 mmol, 8 equiv), thiophenol (327 lL,
3.2 mmol, 32 equiv), and TEA (558 lL, 4 mmol, 40
equiv) were added to provide a solution that was 0.2,
0.8, and 1.0 M in the reagents, respectively. The mix-
ture was shaken for 3 h. The resin was washed with
2· DMF, 2· MeOH, 2· DMF, 2· MeOH, 2· DMF,
and 4· CH2Cl2. Both the color tests (TBNS16 and
dyed-p-nitrophenylglycolate17 tests) gave positive re-
sults (absence of starting material was evaluated by
TLC analysis after cleavage of 10 mg of resin). After
the above-mentioned washing cycles, the resin 21 was
kept under inert atmosphere and used immediately
for the next reaction.
(87 mg, 0.228 mmol,
8
4
0.456 mmol, equiv) and benzoic acid (28 mg,
equiv), DIPEA (78 lL,
0.228 mmol, 4 equiv) were added. The reaction was
shaken for 45 min, then filtered and washed with 2·
DMF, 2· CH2Cl2, THF. The coupling reaction was
repeated four times and after every coupling cycle
the presence of unreacted free amino groups was re-
vealed with dyed-p-nitrophenylglycolate test. Accord-
ing to this method, the amine was revealed by a
colorimetric assay directly on few beads suspended
in 100 lL of a 0.002 M solution of the reagent
(NF31) in MeCN.17 After heating at 70 ꢁC for
10 min in a sand bath, the beads were rapidly washed
with DMF, MeOH, and CH2Cl2 (three times for each
solvent), obtaining resin 24 (R = p-nitrophenyl;
R0 = phenyl). The resin was then cleaved with TFA
20% in CH2Cl2 (2· 20 min) and washed with THF
and CH2Cl2. We recovered 25 mg of crude and, after
chromatography, 11 mg (34% yield) of pure 30. 1H
NMR (300 MHz, CDCl3), d (ppm): 2.06 (m, 1H),
2.42 (m, 1H), 3.61 (m, 1H), 3.71 (m, 1H), 3.68–4.18
(m, 4H), 4.40 (bd, 1H), 4.61 (br s, 1H), 4.73 (br s,
4.11. Functionalization of the free amino group
4.11.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),
6(S),7(S),7a(R) 4-Nitro-benzoic acid 2-(benzoylamino-
methyl)-7-benzyloxy-5-hydroxymethyl-hexahydro-furo[3,2-
b]pyran-6-yl ester (30).
4.11.1.1. Method A. Resin 21 (R = p-nitrophenyl)
(50 mg, loading: 0.56 mmol/g, 0.028 mmol) was suspend-
ed in 2 mL of dry DMF, benzoic acid (7 mg, 0.056 mmol,

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3361
2H), 5.15 (br s, 1H), 7.08 (br s, 1H), 7.32 (m, 8H),
7.61 (m, 2H), 8.02 (m, 4H). HRMS (CI+, CH4) Calcd
for C30H31N2O9 [M+H+]: 563.2030. Found: 563.2035.
(OMe)2C6H3–, or R0 = PhCH2CH2–) (0.50 mmol, 5
equiv), HATU (190 mg, 0.50 mmol, 5 equiv), and DIPEA
(171 lL, 1.00 mmol, 10 equiv) was added to resin 21 (e.g.,
with R = 1-naphthyl-CH2–) (250 mg, 0.4 mmol/g,
0.1 mmol, 1 equiv). Subsequently, the resulting slurry
was shaken for 3 days, the solution was drained, and the
resin was washed with 2· CH2Cl2, 2· DMF and 3·
CH2Cl2. The dyed-p-nitrophenylglycolate test gave a pale
red staining (about 2–5% free amines). A second cycle
with the same quantities was performed for 48 h, then
the solution was drained and the resin was washed with
2· CH2Cl2, 2· DMF, 2· CH2Cl2, 2· DMF, and 3·
CH2Cl2, and dried in vacuo overnight (TNBS test and
the dyed-p-nitrophenylglycolate test were negative after
the second cycle) to obtain a resin type 24. The resin
was cleaved with 20% TFA in CH2Cl2 (2· 2.5 mL,
20 min), and crude compounds 32 (52 mg) and 33
(44 mg) were recovered after evaporation. They were ana-
4.11.2. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Nitro-benzoic acid 7-benzyloxy-2-
heptylaminomethyl-5-hydroxymethyl-hexahydro-furo[3,2-
b]pyran-6-yl ester (31).
4.11.2.1. Method A. A solution of caprylic acid
(44 lL, 0.2 mmol, 4 equiv), DIC (43 lL, 0.2 mmol, 4
equiv), and HOBt (38 mg, 0.2 mmol, 4 equiv) in dry
DMF was stirred for 20 min and added to the suspen-
sion of resin 21 (R = p-nitrophenyl) (100 mg, loading
0.49 mmol/g, 0.049 mmol), DIPEA (96 lL, 0.4 mmol, 8
equiv) in 1 mL of dry DMF. The suspension was shaken
for 45 min, then filtered and washed with 2· DMF, 2·
CH2Cl2, and Et2O, and dried in vacuo for 1 h to get res-
in 24 (R = p-nitrophenyl; R0 = n-heptyl), stored over-
night at ꢀ18 ꢁC. The resin was then cleaved with TFA
20% in CH2Cl2 (2· 20 min) and washed with 2· THF
and 2· CH2Cl2. The cleavage afforded 34 mg of crude
product that, after silica gel chromatography (AcOEt-
hexane 9:1), gave pure amide 31 (4 mg, 15% yield).
1
lyzed by TLC and H NMR, and then purified by flash
chromatography, thus yielding 21 mg (34% yield) of 32
and 14 mg (22% yield) of 33.
1
Compound 32. H NMR (200 MHz, CDCl3), d (ppm):
1.67 (m, 1H), 2.16 (m, 1H), 2.36 (m, 2H), 2.92 (m,
2H), 3.35 (m, 2H), 3.55–3.8 (m, 5H), 4.05 (m, 3H),
4.45 (m, 1H), 4.56 (m, 2H), 4.96 (m, 1H), 5.95 (dt,
1H), 7.1–7.5 and 7.7–7.95 (m, 17H). HRMS Calcd for
C37H40NO7 [M+H+]: 610.2805. Found: 610.2810.
4.11.2.2. Method B. Resin 21 (R = p-nitro) (150 mg,
loading 0.38 mmol/g, 0.057 mmol) was suspended in
4 mL of a mixture of DMF–CH2Cl2 dry 1:2, and HATU
(87 mg, 0.228 mmol,
4
equiv), DIPEA (78 lL,
0.456 mmol, equiv), and caprylic acid (36 lL,
8
1
0.228 mmol, 4 equiv) were added. The reaction was shak-
en for 45 min, and then filtered and washed exactly as in
method C of the previous experimental procedure for
acylation. In the same way and by using dyed-p-nitrophe-
nylglycolate test, we still found the presence of unreacted
amino groups after the fourth coupling cycle, and we thus
proceeded with the fifth one until the test was negative, to
obtain resin 24 (R = p-nitrophenyl; R0 = n-heptyl). The
resin was cleaved with TFA 20% in CH2Cl2 (2· 20 min)
and washed with THF and CH2Cl2. We recovered after
purification amide 31 (9 mg, 27% yield). 1H NMR
(200 MHz, CDCl3), d (ppm): 0.89 (m, 3H), 1.40–1.95
(m, 10H), 2.05 (m, 2H), 2.14 (m, 1H), 2.33 (m, 1H),
3.53 (m, 2H), 3.68–4.39 (m, 5H), 4.61 (m, 1H), 4.75
(br s, 2H), 5.25 (q, 1H), 5.19 (br s, 1H), 6.08 (br s,
1H), 7.49–7.68 (m, 5H), 8.22 (A2X2q, 4 H). HRMS
(CI+, CH4) Calcd for C30H39N2O9 [M+H+]: 571.2656.
Found: 571.2660.
Compound 33. H NMR (200 MHz, CDCl3), d (ppm):
2.03 (m, 1H); 2.35 (m, 1H); 3.37 (m, 2H); 3.58–3.88
(m, 11H); 4.05 (m, 2H); 4.28 (m, 1H); 4.55 (m, 1H);
4.61 (d, 2H, J = 2.7 Hz); 5.0 (m, 1H); 5.9 (m, 1H); 7.1–
7.5 and 7.7–7.95 (m, 17H). HRMS Calcd for
C37H40NO9 [M+H+]: 642.2703. Found: 642.2709.
The following compounds have been prepared by using
the same experimental procedure:
4.12.2. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Cyclopropanecarboxylic acid 7-benzyl-
oxy-5-hydroxymethyl-2-(isobutyrylamino-methyl)-hexahy-
dro-furo[3,2-b]pyran-6-yl ester (34). Crude HPLC assay:
56% (area at 220 nm), isolated yield 19.0 mg (17% over
six steps). 1H NMR (400 MHz, DMSO-d6), d (ppm):
0.82 (m, 4H), 0.97 (m, 6H), 1.59 (m, 1H), 1.65 (m, 1H),
2.11 (m, 1H), 2.36 (m, 1H), 3.05–4.00 (br m, 8H), 4.50
(m, 1H), 4.60 (d, 1H, J = 12.0 Hz), 4.69 (d, 1H,
J = 12.0 Hz), 4.85 (br s, 1H), 4.86 (m, 1H), 7.2–7.35 (m,
5H), 7.67 (br t, 1H). HRMS Calcd for C24H34NO7
[M+H+]: 448.2330. Found: 448.2325.
4.12. Representative procedure for the acylation of the
free NH2 with other carboxylic acids
4.12.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Naphthalene-1-carboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-[(3-phenyl-propionylamino)-meth-
yl]-hexahydro-furo[3,2-b]pyran-6-yl ester (32); 2(R),3a(R),
5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),6(S),7(S),7a(R)
Naphthalene-1-carboxylic acid 7-benzyloxy-2-[(3,5-dime-
thoxy-benzoylamino)-methyl]-5-hydroxymethyl-hexahy-
dro-furo[3,2-b]pyran-6-yl ester (33). This procedure is
essentially similar to the one described in method C for
the preparation of compound 30, but using fewer cycles
with longer reaction times. A 4 mL DMF–CH2Cl2 (1:1 ra-
tio) solution of acid R0COOH (e.g., R0 = 3,5-
4.12.3. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Cyclopropanecarboxylic acid 7-benzyl-
oxy-5-hydroxymethyl-2-[(2-methoxy-acetylamino)-methyl]-
hexahydro-furo[3,2-b]pyran-6-yl ester (35). Crude HPLC
assay: 60% (area at 220 nm), isolated yield 19.9 mg (18%
over six steps). 1H NMR (400 MHz, DMSO-d6), d
(ppm): 0.87 (m, 4H), 1.59 (m, 1H), 2.17 (m, 1H), 2.36
(m, 1H), 3.05–3.8 (br m, 9H), 4.01 (m, 1H), 4.46 (m,
1H), 4.60 (d, 1H), 4.69 (d, 1H), 4.76 (br s, 1H), 4.86 (m,
1H), 7.2–7.4 (m, 5H), 7.66 (br t, 1H). HRMS Calcd for
C23H32NO8: [M+H+] 450.2122. Found: 450.2128.

3362
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
4.12.4. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Propionic acid 7-benzyloxy-5-hydroxy-
methyl-2-(isobutyrylamino-methyl)-hexahydro-furo[3,2-b]py-
ran-6-yl ester (36). Crude HPLC assay: 38% (area at
4.12.9. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Fluoro-benzoic acid 7-benzyloxy-2-
[(2-dimethylamino-acetylamino)-methyl]-5-hydroxymethyl-
hexahydro-furo[3,2-b]pyran-6-yl ester (41). Crude HPLC
assay: 72% (area at 220 nm), isolated yield 2.1 mg (2%
over six steps). 1H NMR (400 MHz, DMSO-d6), d
(ppm): 1.72 (m, 1H), 2.13 (m, 6H), 2.23 (m, 1H), 3.3–
4.0 (m, 10H), 4.52 (m, 1H), 4.61 (d, 1H, J = 12.1 Hz),
4.69 (d, 1H, J = 12.1 Hz), 4.80 (br m, 1H), 5.11 (m,
1H), 7.21 (m, 5H), 7.34 (m, 2H), 7.74 (br m, 1H), 8.01
(m, 2H). MS-ESI m/z = 517.4 (M+H)+. HRMS Calcd
for C27H33FN2O7 [M+H+]: 517.2350. Found: 517.2332.
1
220 nm), isolated yield 22.4 mg (21% over six steps). H
NMR (400 MHz, DMSO-d6), d (ppm): 1.00 (m, 9H),
1.59 (m, 1H), 2.11 (m, 1H), 2.44 (m, 3H), 3.05-4.00 (br
m, 8H), 4.50 (m, 1H), 4.60 (d, 1H, J = 12.1 Hz), 4.69 (d,
1H, J = 12.1 Hz), 4.86 (m, 1H), 5.3 (br s, 1H), 7.2–7.4
(m, 5H), 7.67 (br t, 1H). HRMS Calcd for C23H34NO7
[M+H+]: 436.2330. Found: 436.2334.
4.12.5. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Nicotinic acid 7-benzyloxy-5-hydroxy-
methyl-2-(isobutyrylamino-methyl)-hexahydro-furo[3,2-b]py-
ran-6-yl ester (37). Crude HPLC assay: 70% (area at
4.12.10. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-(isobutyrylamino-methyl)-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (42). Crude HPLC
assay: 66% (area at 220 nm), isolated yield 14.2 mg
1
220 nm), isolated yield 19.4 mg (16% over six steps). H
NMR (400 MHz, DMSO-d6), d (ppm): 0.96 (m, 6H),
1.72 (m, 1H), 2.17 (m, 1H), 2.34 (m, 1H), 3.2–4.0 (m,
8H), 4.57 (m, 1H), 4.61 (d, 1H, J = 12.2 Hz), 4.69 (d,
1H, J = 12.2 Hz), 4.81 (br m, 1H), 5.15 (m, 1H), 7.16 (m,
5H), 7.56 (m, 1H), 7.69 (br m, 1H), 8.24 (m, 1H), 8.80
(m, 1H), 9.06 (s, 1H). HRMS Calcd for C26H33N2O7
[M+H+]: 485.2282. Found: 485.2273.
1
(12% over six steps). H NMR (400 MHz, DMSO-d6),
d (ppm): 0.97 (t, 6H, J = 6.8), 1.72 (m, 1H), 2.15 (m,
1H), 2.34 (m, 1H), 3.15–4.00 (m, 8H), 4.56 (m, 1H),
4.60 (d, 1H, J = 12.1 Hz), 4.69 (d, 1H, J = 12.1 Hz),
4.81 (br m, 1H), 5.06 (t, 1H, J = 7.8 Hz), 7.2 (m, 6H),
7.66 (br t, 1H), 7.79 (m, 1H), 7.96 (m, 1H). HRMS Calcd
for C25H32NO7S [M+H+]: 490.1894. Found: 490.1877.
4.12.6. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Nicotinic acid 7-benzyloxy-5-hy-
droxymethyl-2-[(2-methoxy-acetylamino)-methyl]-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (38). Crude HPLC
assay: 65% (area at 220 nm), isolated yield 21.9 mg (18%
over six steps). 1H NMR (400 MHz, DMSO-d6), d (ppm):
1.72 (m, 1H), 2.23 (m, 1H), 3.21 (s, 3H), 3.4–4.0 (m, 10H),
4.51 (m, 1H), 4.64 (d, 1H, J = 12.1 Hz), 4.67 (d, 1H,
J = 12.1 Hz), 5.14 (m, 1H), 7.20 (m, 5H), 7.55 (m, 1H),
7.68 (br m, 1H), 8.23 (m, 1H), 8.81 (m, 1H), 9.06 (s, 1H).
HRMS Calcd for C25H31N2O8 [M+H+]: 487.2075. Found:
487.2068.
4.12.11. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-benzyl-
oxy-5-hydroxymethyl-2-[(2-methoxy-acetylamino)-methyl]-
hexahydro-furo[3,2-b]pyran-6-yl ester (43). Crude HPLC
assay: 65% (area at 220 nm), isolated yield 16.7 mg
1
(14% over six steps). H NMR (400 MHz, DMSO-d6), d
(ppm): 1.72 (m, 1H), 2.20 (m, 1H), 3.15–4.00 (m, 11H),
4.51 (m, 1H), 4.63 (d, 1H, J = 12.1 Hz), 4.67 (d, 1H,
J = 12.2 Hz), 4.81 (br m, 1H), 5.06 (t, 1H, J = 6.7 Hz),
7.22 (m, 6H), 7.67 (br t, 1H, J = 5.5 Hz), 7.78 (m, 1H),
7.95 (m, 1H). HRMS Calcd for C24H30NO8S [M+H+]:
492.1687. Found: 492.1685.
4.12.7. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Nicotinic acid 7-benzyloxy-2-[(2-dim-
ethylamino-acetylamino)-methyl]-5-hydroxymethyl-hexahy-
dro-furo[3,2-b]pyran-6-yl ester (39). Crude HPLC assay:
65% (area at 220 nm), isolated yield 6.5 mg (5% over six
steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 1.72 (m,
1H), 2.23 (m, 1H), 2.48 (m, 6H), 3.3–4.0 (m, 10H), 4.57
(m, 1H), 4.61 (d, 1H, J = 12.1 Hz), 4.69 (d, 1H, J =
12.1 Hz), 4.81 (br m, 1H), 5.17 (m, 1H), 7.18 (m, 5H), 7.57
(m, 1H), 8.24 (m, 1H), 8.81 (m, 1H), 9.07 (s, 1H). HRMS
Calcd for C26H34N3O7 [M+H+]: 500.2391. Found:
500.2394.
4.12.12. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-benzyl-
oxy-2-[(2-dimethylamino-acetylamino)-methyl]-5-hydroxy-
methyl-hexahydro-furo[3,2-b]pyran-6-yl ester (44). Crude
HPLC assay: 67% (area at 220 nm), isolated yield
6.6 mg (5% over six steps). 1H NMR (400 MHz,
DMSO-d6), d (ppm): 1.71 (m, 1H), 2.20 (m, 1H), 2.52
(s, 6H), 3.15–4.00 (m, 8H), 4.56 (m, 1H), 4.60 (d, 1H,
J = 12.1 Hz), 4.68 (d, 1H, J = 12.1 Hz), 4.82 (br t, 1H),
5.08 (t, 1H, J = 7.7), 7.2 (m, 6H), 7.79 (m, 1H), 7.95
(m, 1H). HRMS Calcd for C25H33N2O7S [M+H+]:
505.2003. Found: 505.1993.
4.12.8. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Fluoro-benzoic acid 7-benzyloxy-5-
hydroxymethyl-2-(isobutyrylamino-methyl)-hexahydro-
furo[3,2-b]pyran-6-yl ester (40). Crude HPLC assay: 80%
(area at 220 nm), isolated yield 18.6 mg (15% over six
4.13. Azide reduction of the carbamoyl derivative and
acylation of the amino group on solid phase
4.13.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Butyl-carbamic acid 7-benzyloxy-5-
hydroxymethyl-2-[(3-phenyl-propionylamino)-methyl]-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (45). Following method
B of azido group reduction, described for the preparation
of the resin-loaded aminoderivative 21, the carbamoyl
derivative resin-linked type 22 (e.g., with R = n-butyl)
was functionalized also in the 3 position through (SnCl2/
1
steps). H NMR (400 MHz, DMSO-d6), d (ppm): 0.96
(m, 6H), 1.73 (m, 1H), 2.17 (m, 1H), 2.33 (m, 1H), 3.0–
4.0 (br m, 8H), 4.55 (m, 1H), 4.60 (d, 1H, J = 12.2 Hz),
4.70 (d, 1H, J = 12.1 Hz), 4.80 (br s, 1H), 5.11 (m, 1H),
7.1–7.2 (m, 5H), 7.34 (t, 2H, J = 8.9 Hz), 7.67 (br t, 1H,
J = 5.4 Hz), 8.0 (m, 2H). HRMS Calcd for C27H33FNO7
[M+H+]: 502.2236. Found: 502.2234.

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3363
PhSH/TEA) reduction of the azide to amine. The result-
ing free amino group was acylated (e.g., with phenylprop-
ionic acid) by working according to the previous
experimental procedure, to give the resin type 24 (with
Y = n-butylNHCO, R0 = 2-phenylethyl). The resin was
cleaved with 20% TFA in CH2Cl2 (2· 2 mL, 20 min),
and compound 45 was recovered after evaporation
(50 mg). The crude compound 45 was analyzed by TLC
0.40 mmol/g, 0.080 mmol) was suspended under inert
atmosphere in dry CH2Cl2 (2 mL), and TEA (11 lL,
0.080 mmol, 1 equiv) and phenyl isocyanate (87 lL,
0.80 mmol, 10 equiv) were added. After the resulting
mixture was shaken for 5 h, the solution was removed
by suction and the resin was washed with 2· CH2Cl2,
2· DMF and 3· CH2Cl2. After the first cycle the TNBS
test was negative, while the dyed-p-nitrophenylglycolate
test, mentioned in the text, gave a pale red staining. A
second cycle with the same quantities was performed
overnight and the resin was washed with 2· CH2Cl2,
2· DMF 2· CH2Cl2, 2· DMF and 3· CH2Cl2 and dried
in vacuo overnight to get a resin type 26. The resin was
cleaved with 20% TFA in CH2Cl2 (2· 2.0 mL, 20 min),
and compounds 47 (40 mg) and 48 (32 mg) were recov-
ered after evaporation. The crude compounds were ana-
1
and H NMR, and purified by flash chromatography.
Twenty-five milligrams of pure 45 was obtained; yield
1
for the five steps: 55%. H NMR (200 MHz, CDCl3), d
(ppm): 0.92 (t, 3H, J = 7.4 Hz), 1.25–1.55 (m, 4H), 1.75
(ddd, 1H, J = 2.5, 5.7, 8.3 Hz), 2.25 (m, 1H), 2.5 (m,
2H), 2.95 (m, 2H), 3.18 (m, 2H), 3.44 (m, 2H), 3.65–
3.86 (m, 4H), 3.97 (m, 1H), 4.13 (m, 1H), 4.51 (m, 1H),
4.72 (s, 2H), 4.84 (dd, 1H, J = 5.0, 5.5 Hz), 4.92 (br t,
1H, J = 5.6 Hz), 6.14 (m, 1H), 7.15–7.4 (m, 10H). HRMS
Calcd for C30H41N2O7 [M+H+]: 541.2908. Found:
541.2887.
1
lyzed by TLC and H NMR, and then purified by flash
chromatography obtaining 10 mg of 47 (22% yield over 5
steps) and 16 mg of 48 (36% yield over 5 steps).
1
4.14. Sulfonylation of the free NH2
Compound 47. H NMR (200 MHz, CDCl3), d (ppm):
1.85 (m, 1H), 2.24 (m, 1H), 2.60 (m, 2H), 2.91 (m,
2H), 3.37–3.65 (m, 5H), 3.72 (m, 1H, H3), 3.85 (t, 1H,
J = 4.3 Hz), 4.12 (m, 1H), 4.54 (m, 1H), 4.68 (m, 2H),
4.91 (dd, 1H, J = 6.0, 5.9 Hz), 5.35 (br t, 1H), 6.68 (s,
1H), 7.1–7.4 (m, 15H). MS (FAB+): m/z = 561 (M++1).
HRMS Calcd for C32H37N2O7 [M+H+]: 561.2595. Found:
561.2584.
4.14.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 3-Phenyl-propionic acid 7-benzyloxy-
5-hydroxymethyl-2-[(4-methoxy-benzenesulfonylamino)-
methyl]-hexahydro-furo[3,2-b]pyran-6-yl ester (46). Res-
in 21 (R = 2-phenylethyl) (200 mg, 0.4 mmol/g, 0.080
mmol) was suspended under inert atmosphere in dry
CH2Cl2 (2 mL) and DMAP (196 mg, 1.60 mmol, 20
equiv), tosyl chloride (153 mg, 0.80 mmol, 10 equiv)
were added. After the resulting mixture was shaken
for 5 h, the solution was removed and the resin was
washed with 2· CH2Cl2, 2· DMF, and 3· CH2Cl2.
After the first cycle, the TNBS test gave a pale red
staining. A second cycle was performed overnight, then
the resin was washed with 2· CH2Cl2, 2· DMF, 2·
CH2Cl2, 2· DMF, and 3· CH2Cl2, and dried in vacuo
overnight (TNBS test was negative after the second cy-
cle) giving a resin type 25. The resin was cleaved with
20% TFA in CH2Cl2 (2· 2.0 mL, 20 min), and com-
pound 46 was recovered after evaporation (40 mg).
1
Compound 48. H NMR (200 MHz, CDCl3), d (ppm):
0.85 (t, 3H, J = 6.7, 6.0 Hz), 1.27 (m, 8H), 1.6 (m,
2H), 1.90 (m,1H), 2.2–2.4 (m, 3H), 3.48 (m, 2H), 3.6–
3.81 (m, 4H), 3.86 (m, 1H), 4.16 (m, 1H), 4.54 (m,
1H), 4.7 (s, 2H), 4.92 (t, 1H, J = 5.9 Hz), 5.38 (br t,
1H), 6.69 (s, 1H), 7.25–7.4 (m, 10H). HRMS Calcd for
C31H43N2O7 [M+H+]: 555.3065. Found: 555.3058.
4.15.2. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Nitro-benzoic acid 7-benzyloxy-5-
hydroxymethyl-2-[(3-phenyl-ureido)-methyl]-hexahydro-
furo[3,2-b]pyran-6-yl ester (49). By working in an
analogous way and by starting from 100 mg of resin 21
(R = p-nitrobenzoyl), the recovered crude product
(25 mg) was chromatographed on silica gel (AcOEt/hex-
ane 9:1) affording the pure ureido-derivative 49 (4 mg,
15% overall yield). 1H NMR (200 MHz, CDCl3) mixture
of diastereoisomers, d (ppm): 2.30 (m, 2H), 3.21–4.30 (m,
8H), 4.61 (m, 1H), 4.71 (br s, 2H), 5.19 (m, 1H), 6.35 (br s,
1H), 6.75 (br s, 1H), 7.3 (m, 10H), 8.2 (m, 4H). HRMS
Calcd for C30H32N3O9 [MH+]: 578.2133. Found:
578.2112.
1
The crude compound was analyzed by TLC and H
NMR, and then purified by flash chromatography.
Six milligrams of pure 46 was thus obtained (yield for
1
the five steps: 12%). H NMR (200 MHz, CDCl3), d
(ppm): 1.73 (m, 1H), 2.17 (m, 1H), 2.43 (s, 3H), 2.68
(m, 2H), 2.95 (m, 2H), 3.25 (m, 2H), 3.55–3.7 (m,
5H), 4.05 (m, 1H), 4.52 (m, 1H), 4.68 (m, 2H), 4.95
(dd, 1H, H4 J = 5.5, 5.4 Hz), 5.07 (m, 1H), 7.15–7.38
(m, 12H), 7.70 (d, 2H, J = 9.2 Hz). HRMS Calcd for
C32H38NO9S [M+H+]: 612.2267. Found: 612.2255.
4.15. Representative procedure for the formation of ureido
derivatives
The following compounds have been prepared by using
the same experimental procedure:
4.15.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 3-Phenyl-propionic acid 7-benzyloxy-
5-hydroxymethyl-2-[(3-phenyl-ureido)-methyl]-hexahydro-
furo[3,2-b]pyran-6-yl ester (47); 2(R),3a(R),5(R),6(S),
7(S),7a(R) and 2(S),3a(R),5(R),6(S),7(S),7a(R) Octanoic
acid 7-benzyloxy-5-hydroxymethyl-2-[(3-phenyl-ureido)-
methyl]-hexahydro-furo[3,2-b]pyran-6-yl ester (48). Resin
21 (R = 2-phenylethyl or R = n-heptyl) (200 mg,
4.15.3. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Cyclopropanecarboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-(3-isopropyl-ureidomethyl)-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (50). Crude HPLC assay:
30% (area at 220 nm), isolated yield 34.9 mg (31% over six
steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 0.82 (m,
4H), 1.0 (m, 6H), 1.59 (m, 2H), 2.10 (m, 1H), 3.1–3.8 (m,
9H), 4.52 (m, 1H), 4.60 (d, 1H), 4.69 (d, 1H), 4.75 (br s,

3364
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
1H), 4.85 (m, 1H), 5.70 (br t, 1H), 5.57 (br m, 1H), 7.28 (m,
5H). HRMS Calcd for C24H35N2O7 [M+H+]: 463.2439.
Found: 463.2449.
4,81 (br m, 1H), 5.16 (m, 1H), 6.27 (m, 1H), 6.67 (m,
1H), 6.98 (m, 1H), 7.17 (m, 6H), 7.4–7.55 (m, 2H), 8.22
(m, 1H), 8.76 (m, 2H), 9.06 (s, 1H). HRMS Calcd for
C29H31FN3O7 [M+H+]: 552.2141. Found: 552.2138.
4.15.4. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Cyclopropanecarboxylic acid 7-ben-
zyloxy-2-[3-(3-fluoro-phenyl)-ureidomethyl]-5-hydroxymeth-
yl-hexahydro-furo[3,2-b]pyran-6-yl ester (51). Crude HPLC
assay: 15% (area at 220 nm), isolated yield 5.8 mg (5% over
six steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 0.82
(m, 4H), 1.59 (m, 1H), 1.71 (m, 1H), 2.17 (m, 1H), 3.2–4.0
(br m, 8H), 4.52 (m, 1H), 4.60 (d, 1H, J = 12.1 Hz), 4.70
(d, 1H, J = 12.1 Hz), 4.76 (br s, 1H), 4.86 (m, 1H), 6.34
(br t, 1H), 6.66 (t, 1H, J = 6.6 Hz), 7.2–7.4 (m, 7H), 7.42
(m, 1H), 7.66 (br t, 1H). HRMS Calcd for C27H32FN2O7
[M+H+]: 515.2188. Found: 515.2177.
4.15.9. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Nicotinic acid 7-benzyloxy-5-hy-
droxymethyl-2-(3-isopropyl-ureidomethyl)-hexahydro-
furo[3,2-b]pyran-6-yl ester (56). Crude HPLC assay: 48%
(area at 220 nm), isolated yield 38.7 mg (31% over six
1
steps). H NMR (400 MHz, DMSO-d6), d (ppm): 0.98
(m, 6H), 1.59 (m, 1H), 2.15 (m, 1H), 3.29 (m, 2H),
3.62 (m, 3H), 3.85 (m, 4H), 4.58 (m, 3H), 4.80 (br s,
1H), 5.14 (m, 1H), 5.76 (br m, 2H), 7.16 (m, 5H),
7.55(m, 1H), 8.24 (m, 1H), 8.80 (m, 1H), 9.06 (m, 1H).
HRMS Calcd for C26H34N3O7 [M+H+]: 500.2391.
Found: 500.2381.
4.15.5. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Cyclopropanecarboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-[3-(3-methoxy-phenyl)-ureidom-
ethyl]-hexahydro-furo[3,2-b]pyran-6-yl ester (52). Crude
HPLC assay: 15% (area at 220 nm), isolated yield 9.6 mg
4.15.10. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Fluoro-benzoic acid 7-benzyloxy-5-
hydroxymethyl-2-(3-isopropyl-ureidomethyl)-hexahydro-
furo[3,2-b]pyran-6-yl ester (57). Crude HPLC assay: 53%
(area at 220 nm), isolated yield 45.8 mg (36% over six
1
(7% over six steps). H NMR (400 MHz, DMSO-d6), d
1
(ppm): 0.82 (m, 4H), 1.59 (m, 1H), 1.71 (m, 1H), 2.16 (m,
1H), 3.2–4.0 (br m, 10H), 4.52 (m, 1H), 4.60 (d, 1H,
J = 12.1 Hz), 4.70 (d, 1H, J = 12.1 Hz), 4.76 (br s, 1H),
4.86 (m, 1H), 6.18 (br t, 1H), 6.45 (m, 1H), 6.82 (m, 1H),
7.05–7.3 (m, 7H), 8.54 (br t, 1H). HRMS Calcd for
C28H35N2O8 [M+H+]: 527.2388. Found: 527.2374.
steps). H NMR (400 MHz, DMSO-d6), d (ppm): 1.00
(d, 6H, J = 8.3), 1.73 (m, 1H), 2.16 (m, 1H), 3.29 (m,
2H), 3.62 (m, 3H), 3.82 (m, 4H), 4.54 (m, 1H), 4.60 (d,
1H, J = 12.1 Hz), 4.69 (d, 1H, J = 12.1 Hz), 4.79 (br m,
1H), 5.10 (m, 1H), 5.76 (m, 2H), 7.18 (m, 5H), 7.34 (m,
2H), 7.99 (m, 2H). HRMS Calcd for C27H34FN2O7
[M+H+]: 517.2345. Found: 517.2333.
4.15.6. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Propionic acid 7-benzyloxy-2-[3-(3-
fluoro-phenyl)-ureidomethyl]-5-hydroxymethyl-hexahydro-
furo[3,2-b]pyran-6-yl ester (53). Crude HPLC assay: 30%
(area at 220 nm), isolated yield 6.0 mg (5% over six steps).
1H NMR (400 MHz, DMSO-d6), d (ppm): 0.97 (t, 3H,
J = 5.5 Hz), 1.70 (m, 1H), 2.26 (m, 3H), 3.15–4.00 (m,
8H), 4.56 (m, 1H), 4.60 (d, 1H), 4.69 (d, 1H), 4.79 (br m,
1H), 4.86 (t, 1H, J = 7.0 Hz), 6.30 (br t, 1H), 6.67 (m,
1H), 7.0–7.4 (m, 7H), 7.42 (m, 1H), 8.82 (br s, 1H). HRMS
Calcd for C26H32FN2O7 [MH+]: 503.2188. Found:
503.2191.
4.15.11. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Fluoro-benzoic acid 7-benzyloxy-5-
hydroxymethyl-2-[3-(3-methoxy-phenyl)-ureidomethyl]-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (58). Crude HPLC as-
say: 30% (area at 220 nm), isolated yield 15.1 mg (11%
over six steps). 1H NMR (400 MHz, DMSO-d6), d
(ppm): 1.73 (m, 1H), 2.20 (m, 1H), 3.10–4.10 (br m,
11H), 4.56 (m, 1H), 4.60 (d, 1H, J = 12.1 Hz), 4.69 (d,
1H, J = 12.1 Hz), 4.80 (br m, 1H), 5.11 (m, 1H), 6.20
(br t, 1H), 6.46 (m, 1H), 6.6–7.35 (m, 10H), 7.99 (m,
2H), 8.53 (s, 1H). HRMS Calcd for C31H34FN2O8
[M+H+]: 581.2294. Found: 581.2294.
4.15.7. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Propionic acid 7-benzyloxy-5-hy-
droxymethyl-2-(3-isopropyl-ureidomethyl)-hexahydro-
furo[3,2-b]pyran-6-yl ester (54). Crude HPLC assay: 45%
(area at 220 nm), isolated yield 37.7 mg (34% over six
steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 1.0 (m,
9H), 1.59 (m, 1H), 2.10 (m, 1H), 2.35 (m, 2H), 3.1–3.8
(m, 8H), 4.52 (m, 1H), 4.60 (d, 1H, J = 12.1 Hz), 4.69 (d,
1H, J = 12.1 Hz), 4.75 (br s, 1H), 4.85 (m, 1H), 5.40 (br t,
1H), 5.75 (br m, 2H), 7.28 (m, 5H). HRMS Calcd for
C23H35N2O7 [M+H+]: 541.2439. Found: 541.2438.
4.15.12. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 4-Fluoro-benzoic acid 7-benzyloxy-
2-[3-(3-fluoro-phenyl)-ureidomethyl]-5-hydroxymethyl-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (59). Crude HPLC assay:
40% (area at 220 nm), isolated yield 22.6 mg (16% over six
steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 1.73 (m,
1H), 2.22 (m, 1H), 3.29–4.0 (br m, 6H), 4.70 (m, 3H), 4.80
(br s, 1H), 5.11 (m, 1H), 6.26 (br t, 1H), 6.67 (t, 1H,
J = 7.2 Hz), 6.99 (m, 1H), 7.2–7.4 (m, 9H), 7.99 (m, 2H),
8.75 (br s, 1H). HRMS Calcd for C30H31F2N2O7
[M+H+]: 569.2094. Found: 569.2090.
4.15.8. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Nicotinic acid 7-benzyloxy-2-[3-(4-
fluoro-phenyl)-ureidomethyl]-5-hydroxymethyl-hexahydro-
furo[3,2-b]pyran-6-yl ester (55). Crude HPLC assay: 50%
(area at 220 nm), isolated yield 17.1 mg (14% over six
steps). H NMR (400 MHz, DMSO-d6), d (ppm): 1.74
(m, 1H), 2.23 (m, 1H), 3.3–4.0 (m, 8H), 4.61 (m, 1H),
4.62 (d, 1H, J = 12.1 Hz), 4.71 (d, 1H, J = 12.1 Hz),
4.15.13. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-(3-isopropyl-ureidomethyl)-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (60). Crude HPLC assay:
60% (area at 220 nm), isolated yield 32.5 mg (26% over six
steps). 1H NMR (400 MHz, DMSO-d6), d (ppm): 1.00 (d,
6 H, J = 6.5), 1.68 (m, 1H), 2.14 (m, 1H), 3.29 (m, 2H), 3.6
1

G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
3365
(m, 3H), 3.84 (m, 4H), 4.58 (m, 1H), 4.62 (d, 1H,
J = 12.1 Hz), 4.70 (d, 1H, J = 12.1 Hz), 4.80 (br m, 1H),
5.05 (t, 1H, J = 7.2), 5.75 (m, 2H), 7.19 (m, 6H), 7.79
(m, 1H), 7.95 (m, 1H). HRMS Calcd for C25H33N2O7S
[M+H+]: 505.2003. Found: 505.1994.
1H), 2.55 (m, 2H), 2.92 (m, 2H), 3.4–3.9 (m, 6H), 3.96
(m, 1H), 4.25 (m, 1H), 4.47 (m, 1H), 4.54 (d, 1H,
J = 11.9 Hz), 4.64 (d, 1H, J = 11.9 Hz), 4.82 (dd, 1H,
J = 6.3, 6.2 Hz), 6.8 (br t, 1H), 7.12–7.38 (m, 15H), 7.6
(s, 1H). HRMS Calcd for C32H36N2O6S [M+H+]:
577.2372. Found: 577.2332.
4.15.14. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-ben-
zyloxy-2-[3-(3-fluoro-phenyl)-ureidomethyl]-5-hydroxymeth-
yl-hexahydro-furo[3,2-b]pyran-6-yl ester (61). Crude HPLC
assay: 45% (area at 220 nm), isolated yield 16.5 mg (12%
over six steps). 1H NMR (400 MHz, DMSO-d6), d
(ppm): 1.73 (m, 1H), 2.20 (m, 1H), 3.2–4.0 (m, 8H), 4.57
(m, 1H), 4.62 (d, 1H, J = 12.1 Hz), 4.70 (d, 1H,
J = 12.1 Hz), 4.81 (br m, 1H), 5.06 (t, 1H, J = 7.2 Hz),
6.26 (br t, 1H), 6.67 (m, 1H), 7.0 (d, 1H), 7.17 (m, 7H),
7.44 (m, 1H), 7.79 (m, 1H), 7.92 (m, 1H), 8.77 (br s,
1H). HRMS Calcd for C28H30FN2O7S [M+H+]:
557.1752. Found: 557.1732.
4.17. Representative procedure for the reductive alkyl-
ation of the free amino group
Resin 21 (R = 2-phenylethyl) (200 mg, 0.42 mmol/g,
0.084 mmol) was suspended under inert atmosphere
in trimethyl orthoformate (TMOF) (2.5 mL) and
the aldehyde (benzaldehyde or p-methoxybenzalde-
hyde) (1.68 mmol, 20 equiv) was added. After the
resulting mixture was shaken overnight at room
temperature, the solution was removed by suction
and the resin was washed with TMOF (2· 4 mL).
After the first cycle, the TNBS test was positive.
Therefore, a second cycle with the same quantities
was performed for 3 h and the resin was washed
with TMOF (2· 4 mL). The resin was suspended
in TMOF (2.5 mL), and AcOH (25 lL, 1% in
TMOF) and NaCNBH3 (106 mg, 1.68 mmol, 20
equiv) were added. The suspension was shaken for
3 h at room temperature, then the solution was
drained and the resin was washed with DMF (2·
3 mL), MeOH (2· 3 mL), 10%TEA/CH2Cl2 (1·
4 mL), MeOH (2· 3 mL), CH2Cl2 (2· 3 mL),
MeOH (2· 3 mL), and CH2Cl2 (2· 3 mL). After
the above-mentioned washing cycles, the resin type
28 (Y = 2-phenylpropanoyl, R0 = benzyl or p-meth-
oxybenzyl) was kept under inert atmosphere and
used immediately for the functionalization of the
secondary amine.
4.15.15. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) Thiophene-2-carboxylic acid 7-ben-
zyloxy-5-hydroxymethyl-2-[3-(3-methoxy-phenyl)-ureidom-
ethyl]-hexahydro-furo[3,2-b]pyran-6-yl ester (62). Crude
HPLC assay: 10% (area at 220 nm), isolated yield
6.7 mg (5% over six steps). 1H NMR (400 MHz,
DMSO-d6), d (ppm): 1.73 (m, 1H), 2.19 (m, 1H), 3.29
(m, 4H), 3.67 (s, 3H), 3.80–4.10 (m, 4H), 4.57 (m, 1H),
4.62 (d, 1H, J = 12.1 Hz), 4.70 (d, 1H, J = 12.1 Hz),
4.81 (br m, 1H), 5.06 (t, 1H, J = 7.1 Hz), 6.19 (m, 1H),
6.46 (br t, 1H), 6.84 (m, 1H), 7.08 (m, 1H), 7.12 (m,
7H), 7.78 (m, 1H), 7.93 (m, 1H), 8.55 (br s, 1H). HRMS
Calcd for C29H33N2O8S [M+H+]: 569.1952. Found:
569.1945.
4.16. Representative procedure for thioureido derivative
formation
4.18. Procedure for the formation of ureido derivatives at
the secondary amino group
4.16.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 3-Phenyl-propionic acid 7-benzyl-
oxy-5-hydroxymethyl-2-[3-(3-methoxy-phenyl)-thioureidom-
ethyl]-hexahydro-furo[3,2-b]pyran-6-yl ester (63). Resin 21
(R = 2-phenylethyl) (120 mg, 0.28 mmol/g, 0.034 mmol)
was suspended under inert atmosphere in dry CH2Cl2
(2 mL), TEA (5 lL, 0.034 mmol, 1 equiv) and phenyl iso-
thiocyanate (41 lL, 0.340 mmol, 10 equiv) were added.
The resulting mixture was then shaken overnight; the
solution removed by suction and the resin washed with
CH2Cl2 (2· 2 mL), DMF (2· 2 mL), CH2Cl2 (2·
2 mL), DMF (2· 2 mL), and CH2Cl2 (4· 2 mL). After
the first cycle, the TNBS test was negative, while the
dyed-p-nitrophenylglycolate test gave a pale red staining.
A second cycle with the same quantities was performed
overnight and the resin was washed with CH2Cl2 (2·
2 mL), DMF (2· 2 mL), CH2Cl2 (2· 2 mL), DMF (2·
2 mL), and CH2Cl2 (4· 2 mL) obtaining a resin type
27. The resin was cleaved with 20% TFA in CH2Cl2
(2· 2.0 mL, 20 min), and compound 63 was recovered
after evaporation (13 mg). The crude compound was
4.18.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 3-Phenyl-propionic acid 2-[(benzyl-
octanoyl-amino)-methyl]-7-benzyloxy-5-hydroxymethyl-hexa-
hydro-furo[3,2-b]pyran-6-yl ester (64). Resin 28 (Y = 2-phe-
nylpropanoyl, R0 = benzyl) (120 mg,
0.28 mmol/g,
0.034 mmol) was suspended under inert atmosphere
in dry CH2Cl2 (2 mL), and TEA (5 lL, 0.034 mmol,
1 equiv) and phenyl isocyanate (37 lL, 0.34 mmol,
10 equiv) were added. After the resulting mixture
was shaken overnight, the solution was removed by
suction and the resin was washed with 2· CH2Cl2,
2· DMF and 3· CH2Cl2. After the first cycle, the
dyed-p-nitrophenylglycolate test gave a pale red stain-
ing. A second cycle with the same quantities was per-
formed overnight and the resin was washed with
CH2Cl2 (2· 2 mL), DMF (2· 2 mL), CH2Cl2 (2·
2 mL), DMF (2· 2 mL), and CH2Cl2 (3· 2 mL),
and dried in vacuo overnight, to obtain a resin type
29. The resin was cleaved with 20% TFA in CH2Cl2
(2· 2.0 mL, 20 min), filtering and solvent evaporation
affording 30 mg of crude product. The crude com-
pound was analyzed by TLC and 1H NMR, and
then purified by flash chromatography. Pure com-
pound 64 were obtained (7 mg, 38% yield for the
1
analyzed by TLC and H NMR, and then purified by
flash chromatography. Pure compound 63 was obtained
(5 mg, 21% yield for the four steps). 1H NMR
(200 MHz, CDCl3), d (ppm): 1.84 (m, 1H), 2.3 (m,

3366
G. Cervi et al. / Bioorg. Med. Chem. 14 (2006) 3349–3367
six steps). 1H NMR (200 MHz, CDCl3), d (ppm):
1.85 (m, 1H), 2.27 (m, 1H), 2.45 (m, 2H), 2.82 (m,
2H), 3.48–3.74 (m, 5H), 3.87 (m, 1H), 3.92 (m,
1H), 4.06 (m, 1H), 4.57–4.75 (m, 5H), 5.0 (dd, 1H,
J = 6.0, 5.9 Hz), 6.95–7.4 (m, 20H), 7.7 (s, 1H).
HRMS Calcd for C39H42N2O7 [M+H+]: 651.3070.
Found: 651.3067.
ment, the plates were processed for the ATPLite-M
assay (Packard) following the manufacturer’s instruc-
tion. Results are expressed as percentage of untreated
control cells.18,19
Acknowledgments
4.19. Procedure for the acylation of the secondary amino
group
This work was supported in part by the European Com-
munity’s Human Potential Programme under contract
HPRN-CT-2002-00173 [GLYCIDIC SCAFFOLDS],
and in part by a FIRB grant (design, preparation, and
biological evaluation of new organic molecules as poten-
tial innovative drugs).
4.19.1. 2(R),3a(R),5(R),6(S),7(S),7a(R) and 2(S),3a(R),
5(R),6(S),7(S),7a(R) 3-Phenyl-propionic acid 7-benzyl-
oxy-2-(1-benzyl-3-phenyl-ureidomethyl)-5-hydroxymethyl-
hexahydro-furo[3,2-b]pyran-6-yl ester (65); 2(R),3a(R),
5(R),6(S),7(S),7a(R) and 2(S),3a(R),5(R),6(S),7(S),7a(R)
3-phenyl-propionic acid 2-{[p-methoxybenzyl-(naphtha-
lene-1-carbonyl)-amino]-methyl}-7-benzyloxy-5-hydroxy-
References and notes
methyl-hexahydro-furo[3,2-b]pyran-6-yl ester (66).
A
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or
p-methoxybenzyl)
(194 mg,
0.28 mmol/g,
0.054 mmol, 1 equiv). Subsequently, the resulting slurry
was shaken for 1 day, the solution was drained, and the
resin was washed with 2· CH2Cl2, 2· DMF, and 3·
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pale red staining. (ca. 2–5% free amines). A second cycle
with the same quantities was performed overnight, then
the solution was drained and the resin was washed with
CH2Cl2 (2· 3 mL), DMF (2· 3 mL), CH2Cl2 (2· 3 mL),
DMF (2· 3 mL), and CH2Cl2 (3 · 3 mL), and dried in
vacuo overnight (the dyed-p-nitrophenylglycolate test
was negative after the second cycle), to get a resin type
29. The resin was cleaved with 20% TFA in CH2Cl2
(2· 2.5 mL, 20 min), and crude compounds 65 (32 mg)
and 66 (63 mg) were recovered after evaporation. The
crude compounds were analyzed by TLC and 1H
NMR, and then purified by flash chromatography
affording pure compounds 65 (8 mg, 23% yield for the
six steps) and 66 (12 mg, 20% yield for the six steps).
1
Compound 65. H NMR (200 MHz, CDCl3), d (ppm):
0.88 (m, 3H), 1.2–1.45 (m, 10H), 1.6–1.8 (m, 3H), 2.3
(m, 1H), 2.62 (m, 2H), 2.92 (m, 2H), 3.5–3.94 (m, 7H),
4.18 (m, 1H), 4.58 (m, 1H), 4.64–4.82 (m, 4H), 4.96 (dd,
1H, J = 7.5, 7.3 Hz), 7.08–7.4 (m, 15H). HRMS Calcd
for C40H52NO7 [M+H+]: 658.3738. Found: 658.3745.
Compound 66. 1H NMR (200 MHz, CDCl3), d (ppm): 1.8
(m, 1H), 2.28 (m, 1H), 2.6 (m, 2H), 2.94 (m, 2H), 3.5 (m,
2H), 3.7–4.0 (m, 9H), 4.12 (m, 1H), 4.26 (m, 1H), 4.52–
4.78 (m, 4H), 4.97 (m, 1H), 6.8–7.02 (m, 4H), 7.12–7.5
(m, 8H), 7.8 (m,3H). MS (FAB+): m/z = 730 ([M+H+]).
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